Harnessing geothermal and piezoelectric properties of stone for sustainable electricity generation

Abstract

This study introduces a novel hybrid system in which piezoelectric and geothermal properties are integrated into basalt and quartz stones to generate green electricity. The same is satisfied by the energy conversion capability, high thermal holding capacity, and the strong piezoelectricity of quartz. This study uses these mechanisms to develop a hybrid system generating constant, reliable, and sustainable energy. The results prove that the system can convert heat into electricity and expand to remote and off-grid areas. The work demonstrates stone heat retention, electric power generation, and integrated system efficiency to provide an accessible, low-cost, scalable alternative to available renewable energy systems. The results present a basis for realizing these properties as an abundant and reliable energy provider and offer a new alternative to traditional renewable technologies.

Introduction

The global transition towards renewable energy significantly drives climate action and fossil fuel reduction. Due to increasing global demands, sustainable, reliable, affordable energy solutions are needed. While solar, wind, and hydropower are important components of the clean energy combination, their distribution and availability will always be limited^1,2. Solar and wind energy, for instance, are intermittent and dependent on weather conditions, while hydropower is geographically limited and can involve significant infrastructure investments^3,4. To some extent, these limitations challenge the magnification of renewable energy to fit the global demand, especially in areas with unideal environmental settings or where infrastructure growth is impossible.

The study addresses energy content in stones like basalt and quartz, suitable for harvesting efficiently and sustainably in remote and off-grid places where low-cost energy solutions are scarce. Available renewable energy systems primarily comprise weather-dependent sources like solar and wind, limiting their implementation in required domains⁵. A breakthrough opportunity lies in the geothermal and piezoelectric characteristics of stones. Despite their abundance and inherent energy-harnessing potential, these properties remain underutilized. Stones such as basalt and quartz, abundant in nature, have revealed potential for energy storage and generation⁶. Geothermal and Piezoelectric properties of stones comprise a revolutionary opportunity. This study investigates a hybrid energy system powered by geothermal and piezoelectric sources to bridge this gap and deliver a scalable and stable energy supply.

Background

The rising global demand for renewable and sustainable energy sources has triggered interest in novel energy-generation technologies⁷. As the world grappled with the impacts of climate change and dwindling fossil fuel resources, piezoelectricity and geothermal energy began to gain traction as potential solutions⁸. Piezoelectric energy harvesting relies on the ability of some materials to generate an electric charge when mechanical stress is applied. Electric charge is produced when mechanical forces, seismic vibrations, and compression are exerted on piezoelectric minerals like quartz and tourmaline⁹. This principle allows for the immediate transformation of surrounding mechanical energy into valuable electrical energy, which is ideal for decentralized energy systems. Geothermal energy harnesses the earth’s natural heat stored in subsurface materials, including rocks. This heat is conducted through basalt and granite, which have high thermal conductivity and storage¹⁰. These stones can absorb heat emitted from the crust of the earth and be used to convert it into steam, rotating the turbines to generate electricity.

Problem statement

Many remote areas and off-grid places — such as those in Nepal’s Himalayan villages or Iceland’s geothermal-rich regions — struggle to find reliable and sustainable energy sources because of challenging terrains and limited infrastructure^11,12. The systems operating on current renewable energy often have limiting environmental dependencies and infrastructure requirements. Due to these constraints, remote, off-grid, and underdeveloped areas frequently lack a reliable renewable energy source¹³. Solar and wind are traditional renewable systems that might not be feasible in some locations because they rely on resources available only for a short period¹⁴. The present work overcomes that gap by proposing a hybrid energy system that uses geothermal heat and piezoelectric properties of stones such as basalt and quartz to offer a continuous, scalable, cost-effective energy solution for these environments.

Significance

• Reliable electricity in remote areas: The proposed hybrid system provides energy access for areas that do not have access to conventional renewable energy sources. Solar, wind, or hydropower infrastructure may not exist in remote, off-grid, or economically underdeveloped regions^15,16. Stones, however, are found almost everywhere on earth, and using them to produce energy could offer power in distant places where it is otherwise inflexible to electrify.

• Decentralized and low-cost energy: The geothermal-piezoelectric system’s capacity for localized energy generation aligns with the growing demand for decentralized power in regions where widespread infrastructure may be impractical^17,18. Therefore, decentralized energy generation can be a profitable substitute for small villages or industries in terms of transmission losses, infrastructure costs, and dependency on centralized power grids.

• Sustainability and environmental impact: This approach is highly sustainable because stones are a renewable and non-depleting resource¹⁹. An innovative and sustainable approach mentioned in the research is integrating geothermal and piezoelectric systems to achieve a clean energy solution and significantly reduce dependence on fossil fuels and carbon emissions with minimum environmental impact²⁰.

Motivation

The motivation for this study is diversifying the world’s energy portfolio. Solar and wind energy have shortcomings like intermittent nature, and hydropower is geographically limited, so there is a constant energy demand^21,22. As demand for scale-up energy continues to rise, demand fluctuations and the challenge of sustaining something like solar or wind energy, so despite being renewable, both can be less cost-effective due to environmental limits^23,24. The systems can lead to new dimensional intra-polar energy generation systems capable of functioning continuously in various environmental conditions. This demonstrates the need for new dimensional energy generation systems. With its novel approach, the study could enable new energy security technologies that promote global sustainability goals.

Research objectives

• Explore the heat-retaining and transferring properties of stones such as basalt and granite to understand their ability to serve as geothermal energy storage materials.

• Investigate the piezoelectric properties of different quartz stones to generate electricity under mechanical stress.

• Design and evaluate an integrated geothermal and piezoelectric energy generation system to ensure a resilient and adaptive power source across different geographical areas.

These objectives are part of a broader vision to develop sustainable and innovative approaches to the global energy crisis.

Literature review

Overview of relevant research

Most research has focused on mainstream renewable energy sources such as solar, wind, hydropower, and biomass²⁵. These technologies have made a big dent in carbon emissions and provided energy security, but they have limitations. Solar and wind are variable, based on environmental conditions; hydropower requires large-scale infrastructure and geography^26,27. In response to these limitations, researchers have explored alternative energy sources, including geothermal energy and piezoelectric technology. Geothermal energy harnesses heat stored beneath the earth’s surface, primarily through hot rocks, magma, and steam. Research in geothermal energy has traditionally focused on deep drilling technologies, geothermal plants, and heat exchange systems using underground reservoirs²⁸. Geothermal power is reliable, but its availability is geographically constrained to regions with high geothermal activity, such as Iceland, parts of the U.S., and Southeast Asia. Piezoelectric energy is generated from mechanical pressure applied to materials like crystals and certain ceramics^29,30. Piezoelectric materials, including quartz and tourmaline, generate electrical charges when subjected to stress or vibration. While piezoelectricity applies to sensors and small-scale devices, its use for large-scale energy generation remains underdeveloped. Recent research has investigated using piezoelectric materials in roadways, bridges, and wearable technology to generate energy from mechanical movements. However, scaling this for consistent energy production is still challenging¹².

The research: geothermal and piezoelectric properties of stone

Research into piezoelectric mechanisms in stone, particularly basalt, granite, and quartz, represents an area of growing interest, as many types of stone have high geothermal energy storage capabilities³¹. Basalt and granite are reported to have good heat retention and heat transfer profiles when heated, which could potentially be used for geothermal energy storage in volcanic areas³². Quartz and tourmaline show piezoelectric properties when subjected to mechanical stress or natural vibrations, such as seismic activity or mechanical pressure. Few studies have examined the hybrid system, which combines a few properties^33,34. Inspired by these findings, this study builds on them by investigating the feasibility of coupling geothermal heat storage and piezoelectric energy harvesting via stone in one decentralized energy system³⁵.

Theories and concepts

• Geothermal energy theory: The core of geothermal energy theory lies around the heat stored below the earth’s surface as transferred to the rocks^36,37. When heat is stored by a rock such as a basalt, the heat can be harnessed and transformed into electricity by steam-driven turbines. This is very much how geothermal plants operate in other parts of the world, such as Iceland and New Zealand.

• Theory of piezoelectric: The piezoelectric effect occurs when mechanical pressure or vibrations cause a few materials, primarily quartz, to produce an electrical charge. This mechanism has been exploited for energy harvesting at the micro-scale level³⁸. Widespread, large-scale applications face challenges such as usage limitations due to material constraints and low efficiency under ambient conditions.

• Hybrid renewable energy systems: Hybrid systems span the combining of variable renewable energy sources to create continuous reliability of power supply. The idea is to harness the strengths of one system when another is not as effective, like solar power during the day and wind energy at night³⁹. This study offers an additional extension of the hybrid energy concept combining geothermal and piezoelectric technologies, in which geothermal heat can serve as a consistent energy source. At the same time, piezoelectricity can generate energy during mechanical acts, such as seismic disturbances or applied stress⁴⁰.

Gaps or controversies in the literature

Several gaps exist in the current literature on the integration of geothermal and piezoelectric energy systems, particularly regarding the use of natural stone as both a heat storage material and a piezoelectric generator:

• Geothermal energy in stones: Research has demonstrated that certain rocks can store geothermal heat, but studies on optimizing heat extraction and conversion in stones like basalt and granite are limited⁴¹. Most geothermal studies focus on liquid reservoirs or engineered systems rather than solid-state geothermal heat storage.

• Piezoelectricity in natural stones: Research on piezoelectric materials has focused primarily on synthetic crystals or engineered ceramics. Although quartz is a known piezoelectric material, studies on the efficiency of natural stones in generating electricity from mechanical stress are sparse^42,43. Furthermore, scaling piezoelectric systems for continuous energy generation remains a technical challenge.

• Hybrid integration: Few studies have proposed hybrid systems that combine geothermal and piezoelectric technologies^44,45. The potential interactions between these two processes, particularly when applied to stone, have not been fully explored. There is a gap in understanding how these technologies can complement each other, especially in areas where geothermal heat and seismic activity or mechanical stress are present⁴⁶.

• Efficiency and scalability: Another gap in the literature concerns energy conversion efficiency in geothermal and piezoelectric systems⁴⁷. Current research has not thoroughly investigated the scalability of these technologies for large-scale power generation, nor has it addressed the challenges of maintaining consistent output in diverse environmental conditions.

Critical framework

The framework of this research is presented in the context of sustainable energy innovation and decentralized energy systems⁴⁸. The approach focuses on naturally abundant materials, such as stone, which aligns with reducing environmental and infrastructural impedances of existing renewable energy systems. This study employs an interdisciplinary framework, merging tenets of geothermal science, material physics (piezoelectricity), and energy systems engineering⁴⁹. The framework also incorporates the concept of energy equity, which focuses on the importance of providing affordable, reliable, and sustainable energy solutions to low-income and underserved areas^50,51. One potential solution is exploring a decentralized hybrid energy system that contributes to the global aim of seamlessly extending energy access in remote and off-grid areas, alleviating energy poverty, and boosting resilience to the impacts of climate change.

This literature review presents a potential perspective on integrating geothermal and piezoelectric properties of stone for electricity generation. Compared to previous studies focusing separately on geothermal or piezoelectric technology, this literature review outlines a unique approach to combining geothermal and piezoelectric energy systems using stone materials. Discussing previous studies and observing the hybrid nature of stones such as basalt and quartz highlights their ability to harness and deliver uninterrupted renewable energy. This study contributes toward a unique and scalable solution for remote and off-grid energy generation, further advancing the field of renewable energy technology above the individual efficiencies offered by earlier studies. The findings highlight the complementary blend’s novelty and promise for improving system efficiency, scalability, and sustainability.

Methodology

This research methodology consists of the following components: stone selection and characterization, geothermal energy extraction, generated energy in piezoelectricity, and hybrid system. Experimental methods and mathematical modeling have been integrated into each phase to examine the system’s performance. Thus, this multidisciplinary study combines knowledge from gel material science, thermodynamics, and piezoelectric physics to develop a novel hybrid energy generation system stone.

Stone selection and characterization

The study focuses on stones that maintain geothermal heat (basalt, granite) and those with prominent piezoelectric characteristics (quartz, tourmaline).

• Thermal characterization: The ability of stones to store geothermal energy is measured using Differential Scanning Calorimetry (DSC), which evaluates the heat retention capacity of stones. The stones’ specific heat capacity (C) and thermal conductivity (k) are these parameters. The equation calculates the heat stored in the stone:

1

Equation (1) calculates the amount of heat energy (Q) stored in the stone. It equals and is calculated by the mass (m) of the stone in kilo-grams times specific (C) of the stone that relates to the amount of energy required to raise 1 kg of the material’s temperature by 1 °C–1 K. It is multiplied by the change in temperature, which is in kelvins (K), representing a difference between the initial and final stone temperature.

• Mechanical property assessment: The piezoelectric stones are subjected to mechanical stress and reaction measures through controlled stress application and resulting piezoelectric charge coefficient (ij​) measurements. The electric charge (p)​ generated under stress calculation as:

2

Equation (2) defines the electric charge (p​) produced by a piezoelectric upon application of mechanical stress. The charge calculation from the piezoelectric coefficient (ij​) in coulombs per newton (C/N) describes the material’s response to mechanical stress multiplied by force (F) applied in newton (N). This equation describes the electric charge generated by applying a mechanical force to a piezoelectric, indicating its ability to convert mechanical stress into electrical energy.

• First law of thermodynamics: A thermodynamic analysis evaluates the thermodynamic efficiency of heat absorption and conversion. The rate of heat transfer Q˙​ through the stone is defined by Fourier’s law of heat conduction:

  3

Equation (3) from Fourier’s law of heat conduction predicts the heat transfer rate (Q˙​)​ through a stone. This rate is assumed in terms of the stone’s thermal conductivity (k), which is a measure of how efficiently the material conducts heat, the cross-sectional area (A) where heat is exchanged, the temperature difference across that area as (ΔT), and the thickness of the stone (d), which opposes this movement of thermal energy. Collectively, these parameters measure the rate at which energy is transferred in a geothermal context.

Geothermal energy extraction

The systems extract heat from stones like basalt and granite. After this, the heat goes through conduction, whereby the stones absorb heat from the earth’s crust, producing steam for electricity generation. Geothermal energy is then utilized to produce steam, powering turbines producing electricity. The thermal efficiency th ​ of the geothermal system is determined using:

4

Equation (4) shows that the thermal efficiency (ηth) of the geothermal system is defined as the work output (W) input in the system versus the heat input (Q). Where (W) is the mechanical or electrical work produced by converting geothermal energy, (Q) is the total thermal energy extracted from the geothermal reservoir. A measure of this is the ability of the system to transform the heat energy into technical work, which is an essential metric for determining system efficiency and improving system performance.

Piezoelectric energy generation

The voltage generation occurs when controlled mechanical stress is applied to piezoelectric stones (quartz, tourmaline), which may be done using seismic vibrations or mechanical compression. The Output Voltage V is related to the force applied as follows:

5

Equation (5) shows the relation between the volume (V) produced by the piezoelectric stone with charge and capacitance. Where (Qp)​ is the electric charge generated due to mechanical stress and (Cp​ )is the capacitance of stone. The relationship shows that increasing the value of electric charge while decreasing with greater capacitance. It emphasizes that piezoelectric stones such as quartz and tourmaline can efficiently convert mechanical stress into electrical energy.

• Scaling the piezoelectric system: The potential of scaling the piezoelectric system is analyzed by simulating different pressure sources based on seismic vibrations and mechanical compressions and their subsequent achievable total power output ():

  6

Equation (6) assesses the scalability of the piezoelectric power generation system, addressing the total generated power (Pp​) given the power generated by voltage (V) and the electrical resistance of the system (R). V is the voltage that piezoelectric stones develop due to stress, and R is the circuit’s resistance. This equation calculates the amount of power the system could generate by simulating different pressure sources, such as seismic vibrations or mechanical compressions. It indicates whether it is suitable for large-scale energy generation applications.

In piezoelectric energy harvesting, mechanical stress would affect the electrical output according to Eqs. (5) and (6).

Hybrid system development

The hybrid system development integrates geothermal and piezoelectric energy harvesting systems into a combined system where energy generation depends on environmental conditions. The total energy produced is a combination of the geothermal energy being harvested from heat and piezoelectric energy, which is created from mechanical stress, leading to uninterrupted energy production:

7

The total energy output (total​) of the hybrid system is given by Eq. (7), which calculates the contribution from the geothermal and piezoelectric subsystems. The overall energy produced will comprise the geothermal energy (geo​) generated by the heat of the stones and the piezoelectric energy (piezo​) produced by mechanical stress, such as during a seismic event. This equation models a hybrid optimization used to analyze the aspects of integrated energy methodologies that provide a consistent, managed supply that returns energy to renewable combinations through environmental condition alteration.

Data collection and analysis

Data collection and analysis gather thermal performance metrics through heat retention, heat conduction, and the efficiency of converting geothermal heat into electricity from the stones. It also includes the voltage and power output under mechanical stress on piezoelectric stones, with the results used for scalability estimates and simulating the hybrid system energy output, reliability, and efficiency under variable real-world heat and stress conditions.

This methodology comprehensively assesses the feasibility and efficiency of implementing stone as a renewable energy source through a hybrid geothermal-piezoelectric energy generation structure.

Stone selection and characterization

The stones are selected and characterized based on their heat retention qualities and piezoelectric properties. The figures below summarize the key thermal and mechanical properties determined by Differential Scanning Calorimetry (DSC) and piezoelectric charge coefficient measurements.

Thermal characterization

The thermal properties of stones, like basalt and granite, are measured to determine heat retention and conductivity. Figure 1 summarizes the main parameters used to select the stones.

Fig. 1.

Parameters for the selected stones.

The thermal properties of basalt, granite, limestone, and marble to evaluate their suitability for geothermal heat storage are presented in Fig. 1. Both basalt and granite have high specific heat capacities and significant thermal conductivity, making them perfect for geothermal energy storage. Basalt specific heat capacity = 840 , thermal conductivity = 1.9 , and granite specific heat capacity = 790 and thermal conductivity = 2.5 , respectively. Basalt (252,000 J) has a marginally higher heat retention than granite (237,000 J), suggesting more storage capacity. Limestone and marble have a high specific heat capacity but low thermal conductivity, which makes them less responsive in heat exchange than basalt and granite. Generally, basalt and granite are the most promising materials for geothermal applications.

Mechanical characterization (Piezoelectric Properties)

The stones are characterized by their ability to generate an electrical charge under mechanical stress for piezoelectric energy generation. Figure 2 below summarizes the piezoelectric charge coefficient and corresponding charge output for selected stones like quartz and tourmaline. Tourmaline and quartz demonstrate significant potential for piezoelectric energy generation, with the highest charge output.

Fig. 2.

Piezoelectric properties of various stones.

Figure 2 summarizes the piezoelectric properties of various stones, showing their ability to generate electrical charge under mechanical stress. Tourmaline has the highest piezoelectric coefficient at 4.1 , leading to the highest electric charge output (4.1e-9 C) and voltage (0.41 V) when a 1000 N force is applied. With a coefficient of 2.3 , quartz generates 2.3e-9 C and 0.23 V, making it slightly less efficient than tourmaline but still a strong candidate for energy generation. Other materials like topaz and zinc oxide show lower or significantly higher outputs. Zinc oxide, with the highest coefficient (12 ), generates the most significant charge (12e-9 C) and voltage (1.2 V), but other factors may limit its practical application. Tourmaline and quartz demonstrate significant potential for piezoelectric applications, especially in energy harvesting.

Stone suitability

This analysis indicates that basalt and granite are highly suitable for geothermal heat storage due to their strong thermal properties but low piezoelectric suitability. Quartz and tourmaline are less effective thermally but excel in piezoelectric properties, with tourmaline being the best choice for energy generation under mechanical stress. The hybrid geothermal piezoelectric system draws on basalt or granite for geothermal energy storage and tourmaline for piezoelectric energy harvesting to provide a balanced method of energy generation. All these aspects set the grounds for hybrid system design, where geothermal and piezoelectric sources are integrated to improve the energy output.

Basalt, granite, and quartz were selected for characteristics important to hybrid energy generation. Because basalt (thermal conductivity: 1.5–2.5 W/m·K) and granite (2.5–3.5 W/m·K) have such high thermal conductivity and heat retention, these are excellent for geothermal applications as these absorb and hold geothermal heat^52,53. Quartz was selected as the material due to its excellent piezoelectric properties (d11 ≈ 2.3 pC/N), allowing it to efficiently convert mechanical stress — from seismic tremors or mechanical compression — into electricity and harvest energy from mechanical deformation⁵⁴. Such a combination improves the system’s efficiency using geothermal energy and piezoelectric mechanisms.

Geothermal energy extraction

In geothermal energy extraction, stones such as basalt and granite are heat storage media. These stones absorb heat from the earth’s crust and heat water to create steam to turn turbines, which produce electricity. The stones’ thermodynamic performance is analyzed based on their heat absorption, storage, and conversion rate.

Heat absorption and storage

Figure 3 below summarizes the key parameters involved in the heat absorption and storage for selected stones (basalt, granite, limestone, and marble). The thermodynamic analysis focuses on how much heat each stone can absorb and store based on its specific heat capacity, thermal conductivity, and applied temperature gradient. Limestone shows the highest heat absorption due to its high specific heat capacity. At the same time, basalt and granite are preferred for their balance of heat absorption and thermal conductivity, making them more efficient for energy transfer.

Fig. 3.

The Thermodynamic analysis with different stone.

Temporal heat conduction for basalt, granite, limestone, and marble is shown in Fig. 3, and its use is based on their thermal conductivity, heat capacity, and temperature difference. Limestone absorbs the most heat (276,000,000 J) - its high specific heat capacity (920 ) makes it suitable for storing heat. However, basalt and granite absorb less heat (252,000,000 J and 237,000,000 J, respectively). Still, they also achieve a better heat absorption and thermal conductivity trade-off, which would be a more efficient energy transfer medium for geothermal applications. Marble soaks up 258,000,000 J, putting it between basalt and limestone. These findings imply that basalt and granite are the best candidates for geothermal energy storage based on thermal conductivity, while limestone is better for heat retention.

Heat transfer and steam generation

The heat transfer rate from the stones to the surrounding medium is critical for efficient steam generation. The simplified turbine system and summarizing heat transfer properties and amount of steam produced per stone can be seen in Fig. 4. The amount of steam produced is estimated according to the heat energy transferred to water (1 kg of water takes approximately 2260 kJ of heat energy to convert to steam). Turbine power generation is measured using the steam volumetric flow, with a 50% conversion efficiency. Granite shows the most significant heat transfer rate and associated steam generation, maximizing energy available to the turbine, especially for geothermal applications.

Fig. 4.

Heat transfer properties with different stones.

Figure 4 summarizes the heat transfer and steam generation data for basalt, granite, limestone, and marble. Granite exhibits the highest heat transfer rate (12,500 W), resulting in the greatest steam generation (0.18 kg/s) and turbine power output (90 kW), making it the most efficient stone for steam production. Basalt, with a slightly lower heat transfer rate (9,500 W), generates 0.14 kg/s of steam and produces 70 kW of power, performing well in geothermal energy systems. Limestone and marble produce minimal steam, with limestone yielding 0.09 kg/s and a power output of 45 kW, but marble creates 0.16 kg/s and 80 kW. These results suggest that granite is the most effective stone for steam generation and turbine power output.

Thermal efficiency

The thermal efficiency of the geothermal energy extraction system is critical for evaluating the overall performance of the stones in converting stored heat into mechanical energy for electricity generation. Figure 5 shows the geothermal system and details the thermal efficiency of each stone. Assume that the system’s efficiency is fixed at 50%, wherein half of the heat from the stones is turned into mechanical work for electricity production. The stones would have identical efficiencies, but their total work done depends on how much heat can be absorbed.

Fig. 5.

Thermal efficiency of the geothermal system for various stones.

The thermal efficiency of the geothermal energy extraction system for basalt, granite, limestone, and marble is shown in Fig. 5. All stones have thermal efficiency (50%); thus, electricity is produced from half of the absorbed heat. However, the work varies depending on how much heat each stone can absorb. Limestone captures the most energy (276,000,000 J), produces the most work (138,000,000 J), and is followed by marble (129,000,000 J), basalt (126,000,000 J), and granite (118,500,000 J). All stones are equivalent in terms of thermal efficiency. Limestone has the highest intrinsic energy potential for energy output due to its superior heat absorption capacity.

Geothermal energy extraction suitability

This analysis provides an overall ranking of the stones based on their heat absorption, transfer rate, steam generation, and turbine power output.

• Granite is the most suitable stone for geothermal energy extraction, with a high heat transfer rate and steam generation capacity, leading to high power output.

• Basalt is also a strong candidate due to its efficient heat absorption and power output potential.

• Limestone shows the highest heat absorption but falls short in heat transfer and steam generation, making it less effective for turbine-based energy generation.

System efficiency in fluctuating geothermal regions

The fluctuating geothermal regions present challenges due to varying heat flow and inconsistent thermal energy availability. The proposed hybrid geothermal-piezoelectric energy system can benefit from using adaptive strategies to increase effectiveness and achieve optimal performance. These strategies identify the purpose of stabilizing output, maximizing energy capture, and minimizing downtime due to unpredictable geothermal activity.

• Developing real-time monitoring and adaptive control: Real-time monitoring and adaptive control are realized through high-sensitivity temperature and piezoelectric sensors. This further allows real-time tracking of subsurface heat, mechanical stress, or seismic activity. The temperature sensors facilitate real-time adjustments in heat extraction, optimizing geothermal energy usage, whereas the piezoelectric sensors ensure quick responsiveness to stress and vibrations⁵⁵. This sensor data is processed in real-time by a smart Energy Management Unit (EMU) that automatically switches the geothermal and piezoelectric energy harvesting subsystems depending on the environmental conditions.

• Hybridization with other renewable energy sources: In regions with high solar insolation, solar panels can enhance power in cases of reduced geothermal activity. Wind Turbines — Wind turbines can add stability, especially within the geothermal activity zones and high wind current areas. Excess energy produced during peak geothermal or piezoelectric activity is stored in advanced battery systems ( lithium-ion or flow batteries) for continuous power delivery⁵⁶.

• Optimizing heat extraction techniques: The Optimization of heat extraction techniques lies in enhanced geothermal systems, where fluid is injected into hot rock formations to enhance rock permeability to allow for a more efficient heat transfer by the rocks and to stabilize energy output in times when subterranean heat levels themselves change⁵⁷. This approach increases the usable heat that can be converted to energy. Thermally insulated pipelines and stone chambers are dynamically significant in reducing heat loss during transport and storage, further promoting the operational efficiency of the geothermal subsystem. Several innovative solutions have been implemented to improve the overall efficiency and sustainability of the geothermal energy harvesting process.

• Dynamic load management: This aspect focuses on coordinating the system’s energy generation in high dependence on real-time demand, often through implementing demand response programs and providing when needed, enabling efficient production and supply of energy without unnecessary waste. Energy production is tailored according to energy consumption profiles, which leads to resource usage optimization. The system’s modular nature enables component scalability, wherein individual units can be turned on or off based on the present geothermal conditions and energy demand. It also guarantees that the system will adjust to changing energy needs, all while staying energy-efficient and eco-friendly.

The proposed hybrid energy system has the potential to enhance efficiency and stabilize output in fluctuating geothermal regions dramatically by integrating real-time monitoring, renewable hybridization, optimized heat extraction, and adaptive load management.

This analysis determined granite as the best stone for recovering geothermal energy since they have high conductivities for thermal and steam and sufficient power output when fed into a turbine. Basalt is also a strong contender, with high heat absorption and moderate production. Marble is relatively in between; it is quite promising but less efficient than granite and basalt. Thus, limestone in heat absorption is weak due to low heat transfer and steam generation, which is less efficient for geothermal energy production.

Piezoelectric energy generation

In this research phase, stones with strong piezoelectric properties (like quartz and tourmaline) are subjected to controlled mechanical stress, such as pressure from seismic vibrations or mechanical compression, to assess their electricity generation capacity. The results are captured through the voltage output, and scalability is analyzed based on varying forces applied to the stones.

Piezoelectric properties under mechanical stress

Figure 6 summarizes the electricity generation capacity of selected piezoelectric stones under varying mechanical stresses. The piezoelectric charge coefficient, applied force, electric charge generated, and voltage output are provided. Tourmaline exhibits a higher piezoelectric coefficient and thus generates more electrical charge and higher voltage output than quartz under the same mechanical stress.

Fig. 6.

Electricity generation capacity analysis with selected piezoelectric stones.

Figure 6 shows the piezoelectric characteristics of quartz and tourmaline upon applied mechanical stress. Both stones display higher electric charge and voltage output when the applied force increases. Compared to quartz (2.3 ), tourmaline has a higher piezoelectric coefficient (4.1 ), thus generating a greater electric charge and voltage under a similar force (F) applied. At 1000 N, tourmaline yields 4.1e-9 C and 0.41 V compared to quartz, which only yields 2.3e-9 C and 0.23 V for the same force. In contrast, at 5000 N, tourmaline yields 20.5e-9 C and 2.05 V compared to 11.5e-9 C and 1.15 V for quartz, thus concluding the more efficient nature of tourmaline over quartz piezoelectricity generation, indicating viability in a high-stress environment.

Scalability analysis

Different magnitudes of force are applied to each stone to evaluate the scalability of piezoelectric energy generation, and the resulting electric charge and voltage output are recorded. Figure 7 below shows how the system scales with increasing force.

Fig. 7.

Scalability of piezoelectric energy generation.

Figure 7 shows the scalability of piezoelectric energy generation for quartz and tourmaline under increasing mechanical stress as the force applied increases and the electric charge, voltage output, and power output scale accordingly. Tourmaline consistently produces higher charge and voltage than quartz for the same force. For case, at 10,000 N, tourmaline generates 41e-9 C, 4.1 V, and 0.841 W, while quartz produces 23e-9 C, 2.3 V, and 0.529 W. This shows tourmaline has better scalability in terms of power output. Both materials exhibit a linear increase in power output with force, but tourmaline provides higher energy efficiency and is thus more suitable for large-scale piezoelectric energy generation. As the force increases, the power output scales up for both quartz and tourmaline, with tourmaline consistently generating more power due to its higher piezoelectric coefficient. Tourmaline is, therefore, better suited for large-scale piezoelectric energy generation systems.

Block diagram of piezoelectric energy generation system

The block diagram (Fig. 8) above depicts the flow of piezoelectric energy conversion from mechanical stress to electricity.

Fig. 8.

Piezoelectric Energy Generation System.

• Mechanical stress (Input): This input initially causes the system to apply mechanical stress. It can be seismic vibrations or other external forces applied to the piezoelectric material.

• Piezoelectric stone (Quartz/Tourmaline): Define the piezoelectric stone that mediates the mechanical stress for the quartz or tourmaline in eventual construction; it generates an electric field when exposed to a mechanical field (applying stress) in a way for its mechanical modification.

• Generation of electric charges: The mechanical stress applied on the piezoelectric material leads to the generation of an electric charge proportional to the force exerted on it.

• Voltage output monitoring: It converts the electrical charge into a voltage output. The output voltage is continuously monitored for proper operation, and the generated energy is stored.

• Power output (Electricity): The generated voltage generates electricity that can be harnessed for energy generation, stored, or fed into the power grid.

The following is the block diagram of the process, from applying mechanical stress to generating electricity in the piezoelectric system.

Electrical energy generation from piezoelectricity

Quartz and tourmaline are piezoelectric materials that generate an electric charge when mechanical stress is applied. This happens when the charges are displaced in the crystal lattice. External pressure or stress is applied to the material that polarizes its internal structure and generates a potential difference. This charge is collected by electrodes placed on the material to convert it into usable electrical energy. It works exceptionally well for harnessing energy from vibration, seismic activity, or mechanical compression.

Geothermal heat utilization

Geothermal energy depends on the heat trapped in the earth’s crust. Heat rises from the earth’s interior to the surface, transferred through high-thermal-conductivity materials such as basalt and granite. In energy systems, geothermal heat is transferred to a working fluid, typically water, which vaporizes into steam. The steam then rotates turbines interconnected to generators, generating electricity. This response of materials’ heat storage and conductivity capacity keeps the efficiency high in transferring the heat. These systems work best in environments with elevated geothermal gradients, such as volcanic or tectonic regions.

Piezoelectric energy generation suitability

This analysis emphasizes quartz and tourmaline’s potential for use in piezoelectric energy generation. The present study verified that tourmaline always performs better than quartz in terms of electric charge, voltage output, and power output under universal conditions, making tourmaline the most efficient piezoelectric energy harvesting material. Compared to quartz, which performs moderately in each category. This analysis confirms that tourmaline is more scalable and efficient for applications requiring high power and energy harvesting under mechanical stress. This suggests a tremendous potential for large-scale use in environments with significant force or vibration.

Comparison of piezoelectric materials

The comparative analysis of piezoelectric materials, where quartz, tourmaline, and Rochelle salt have different properties concerning piezoelectric coefficients, thermal stability, and mechanical durability, is essential for energy generation applications presented in Table 1.

Table 1.

Piezoelectric materials.

Material	Piezoelectric coefficient (d < sub > 11</sub> )	Thermal stability	Mechanical durability
Quartz	3 × 10 < sup > − 12</sup > m/V	High	High
Tourmaline	Approximately 1.5 times that of quartz	High	High
Rochelle Salt	Higher than quartz	Low	Low

• Quartz: Quartz’s has a piezoelectric coefficient of around 3 × 10 < sup > − 12</sup > m/V with excellent mechanical durability and thermal stability, boosting more stable products following various environmental conditions⁵⁸.

• Tourmaline: The piezoelectric constants of tourmaline are at least 1.5 times those of α-quartz, revealing a higher piezoelectric response⁵⁹. However, its intricate crystal structure can make it more difficult to process this material.

• Rochelle salt: Although Rochelle salt has a more significant piezoelectric effect than quartz, it has poor thermal stability and mechanical durability, making it less applicable⁶⁰.

Quartz has sufficient piezoelectric efficiency, thermal stability, and mechanical durability, enabling it to be reliably used in durable energy generation systems.

Hybrid system development

The proposed hybrid energy generation system (Fig. 9) integrates geothermal and piezoelectric mechanisms to ensure constant electricity generation under environmental conditions. The fraction of the geothermal model works during underground heat availability, and the piezoelectric model works in response to mechanical stresses such as seismic vibrations. This proposed system is designed for areas with variable energy sources. It ensures a more stable and sustainable energy supply.

Fig. 9.

Schematic diagram of the hybrid system.

System architecture

The hybrid energy generation system architecture integrates geothermal and piezoelectric technologies for efficient and adaptive energy harvesting as environmental conditions change:

Geothermal subsystem

• Heat source: Extracts thermal energy from the earth’s crust.

• Type of stone: Basalt and granite are used for robust heat retention and thermal conductivity.

• Energy transformation: Stones take in geothermal heat, which creates steam for turbine power to generate a current.

Piezoelectric subsystem

• Pressure source: Harnesses on-site vibrations (seismic reconnaissance or construction freeze) and applied mechanical compression activity.

• Stone used: Quartz & Tourmaline – Known for High Piezoelectric Efficiency.

• Energy transformation: It translates tension to an electrical charge that will be treated into electrical energy.

Hybrid control system

• Sensors: Environmental variables such as temperature (geothermal) and stress (piezoelectric systems).

• Energy management unit: This unit ensures that all the subsystems work together — switching from or combining either one is operational at the exact moment to output a steady flow of energy dynamically.

This architecture takes advantage of the complementary strengths of both systems to maximize energy generation under different conditions.

Operational flow

The hybrid system’s operation is depicted in this configuration, based on geothermal energy utilized when underground heat is sufficient. In contrast, piezoelectric energy is generated when seismic vibrations or mechanical stress is detected. The EMU allows the transfer of power generation between the two subsystems, preventing an interruption in energy supply. A block diagram (Fig. 10) describing the integration of geothermal and piezoelectric energy generation subsystems under the control of an Energy Management Unit (EMU) in a Hybrid system. The process diagram can thus be broken down as follows:

Fig. 10.

Hybrid system operation.

• Environmental inputs: There are two types of inputs that a system receives:

1. Geothermal energy source comes from the heat of the earth.

2. Vibrations of seismic activities are applied externally to the piezoelectric materials. External mechanical stress is exerted on the piezoelectric, such as from vibrations induced by seismic actions.

• Geothermal subsystem: This system generates energy from underground heating through geothermal processes like heat transfer from the earth’s crust to the stones.

• piezoelectric subsystem: This subsystem utilizes the principle of piezoelectricity as certain materials convert mechanical stress to charge, and seismic activity applies mechanical stress as the materials like quartz or tourmaline will generate charge when placed in mechanical stress, and the stress is converted into electrical energy.

• Energy management unit: The energy management unit receives energy from both subsystems and adapts the power output according to the environmental conditions, ensuring energy is integrated seamlessly and supplied consistently.

• Constant power output: The energy management unit routes the energy produced by both subsystems to constant power production. This continuous power output can be utilized for energy supply, storage, and grid integration.

This system provides consistent and reliable power generation by coupling geothermal and piezoelectric energy sources and integrating them with intelligent management of the environmental inputs.

Scalability and continuous operation

• Geothermal system activation: If deep heat conditions remain stable, the geothermal system produces a basal power output, ensuring baseline electricity production.

• Piezoelectric system activation: In periods of stress, such as earthquakes and seismic activities, the piezoelectric system activates and generates supplementary power for the geothermal system.

• Continuous power supply: The hybrid solution can deliver uninterrupted power as both systems can be combined, which offers an alternative to geothermal heated zones with short-term seismic activity.

This proposed hybrid energy system is a reliable and sustainable energy generation solution for areas with unpredictable environmental characteristics as long as geothermal resources are sufficiently available. Most of the energy needed is retrieved from underground heat, and they exploit the difference in mechanical stress to increase the performance, thus at the same time enabling stable power generation even insulated from the grid to serve as an extra energy source in remote areas. These strategies combined produce an unprecedented energy source that fixes the previous limitations of ordinary renewables and offers a scalable solution for upcoming energy requirements.

Results

This section focuses on the performance of the various stone types for geothermal electricity generation and piezoelectric energy generation. The analysis also encompasses the performance of the hybrid geothermal-piezoelectric system under aspects like output power, scalability, and cost-effectiveness.

Generation of electricity from geothermal sources and heat retention

The geothermal system relies on natural stones like basalt and granite to store geothermal energy and produce steam to turn turbines and generate electricity.

Figure 11 exposes basalt’s superior heat retention efficiency at 65%, allowing it to maintain temperature longer than granite, which is only 58%. Basalt cooled down by 50 °C in 180 min, while granite took only 150 min at the same starting point of 300 °C, indicating that basalt can maintain heat longer than granite, making basalt more suitable for geothermal energy storage. The longer cooling time stabilizes energy transfer for geothermal uses, giving basalt the advantage over systems that need longer-duration heat storage to continue producing energy. In contrast, the lower retention efficiency shown for granite indicates the suitability of these materials for such applications that demand constant thermal performance, directly aiding the selection of materials to derive geothermal system designs.

Fig. 11.

Comparison of Heat retention.

Geothermal electricity production

Basalt and granite heat in the geothermal chamber converts steam to electricity. The power production over time evaluates the efficiency of stones in energy conversion.

Figure 12 shows basalt performing significantly better in geothermal energy conversion at 50 kW vs. granite at 45 kW. The greater output can be attributed to basalt’s superior hold on heat and a steam flow rate of 0.8 kg/s compared to 0.7 kg/s for granite. The system’s conversion efficiency using basalt (70%) surpasses granite’s 65%, further reinforcing basalt’s suitability for geothermal applications. The result of basalt significantly improves the consistency and output of input energy in its production, making it favourable as a material for more efficient energy output in geothermal systems. Granite is a viable option, although slightly less efficient, as long as applications do not require high efficiency.

Fig. 12.

Efficiency in geothermal energy conversion.

Piezoelectric energy generation

These piezoelectric stones, such as quartz and tourmaline, generated an electric current for testing different mechanical stresses. The tests accurately control simulated seismic events and mechanical stress.

Electric potential under the action of mechanical stress

The strain mechanical stress rig exerted forces of 1000 N,000 to 10,000 N on quartz and tourmaline. The voltage measures at several different force levels.

The results show that quartz outperforms tourmaline in voltage and power output under varying mechanical stresses. In Fig. 13, the voltage output of quartz is consistently higher at all force levels. The study decided that at a force of 10,000 N, the quartz seed rocked 2.3 V more than the tourmaline (1.95 V), highlighting quartz’s superior piezoelectric response and thus also its ability to convert applied mechanical stress into stored electrical potential. As a similar trend, Fig. 14 shows that the power output achieved was 0.529 W for quartz at a stimulation load of 10,000 N; instead, the same load applied to tourmaline allowed to produce only 0.414 W. All these results point to the greater energy conversion efficiency of quartz compared to tourmaline, making them suitable for applications where it is possible to harvest high mechanical stress and convert it into electricity. Thus, compared to other materials, quartz has better piezoelectric properties, indicating that a piezoelectric system made of quartz would be more efficient at harvesting energy.

Fig. 13.

Voltage Output.

Fig. 14.

Power output.

Real-world environment performance

The piezoelectric stones in real-world environments simulate seismic activity and construction vibrations, assessing their real-world applicability.

The experimental results show that traditional materials used in piezoelectric energy harvesting perform better in moist and humid environments. The seismic environment produced about 160%, and the construction environment produced about 138% higher outputs in comparison to the construction environment from Fig. 15, where, for the seismic region, voltage (1.56 V) and power output (0.389 W) are higher than in construction region (voltage (0.88 V) and power (0.165 W)). Even though there are lower outputs in construction areas, the data mentioned illustrates the practical potential for energy harvesting in less intense environments. Further, the supports experienced higher vibration frequencies (6 Hz) and larger applied forces (7000 N) in seismic areas. The rest continuous support with seismic location having (6 Hz) vibration frequency and higher applied force (7000 N), while construction location with lower forces (3000 N) and (3 Hz) frequency as seen in Fig. 16. These results further highlight that piezoelectric harvesting can succeed more in seismic areas with incredible vibrations and mechanical stress. It also highlights that location-specific considerations are necessary to maximize energy harvesting efficiency.

Fig. 15.

Comparison between seismic and construction environments.

Fig. 16.

Seismic regions with higher vibration frequencies.

Performance of hybrid geothermal-piezoelectric system

The geothermal and piezoelectric subsystems combine to develop a hybrid system that generates continuous and reliable energy production. The figures are evaluated during tests on the combined system at different heat and stress conditions.

These results illustrate the flexibility and effectiveness of the hybrid geothermal-piezoelectric setup across diverse conditions. The current generation efficiency of 70% at a power output of 110 kW in high-heat, high-stress scenarios is illustrated in Fig. 17. This reflects that the system functions at its best when the geothermal and piezoelectric subsystems are utilized to their full potential. 55 kW was produced at low heat and high stress, demonstrating the piezoelectric subsystem’s ability to supplement low geothermal output. This highlights the hybrid system’s adaptability and capability to sustain power generation despite changing geothermal heat. The versatility seen previously in Fig. 18 is further confirmed by the unified common ground, with geothermal power dominating high-heat low-stress environments and piezoelectric power dominating low-heat high-stress environments. This feature allows the device to generate power consistently, seamlessly transitioning between geothermal and piezoelectric modes of operation, emphasizing the merits of using piezoelectric generators in combination with geothermal systems in a hybrid system.

Fig. 17.

Performance analysis in a Hybrid system.

Fig. 18.

Geothermal and piezoelectric power dominated various conditions.

Scalability and cost-effectiveness

• Scalability: The system is scalable regarding geothermal heat availability and mechanical stresses. The hybrid system scales up to serve more significant energy demands in geothermal-rich areas with enough seismic activity.

• Cost-effectiveness: The system is competitive with traditional renewables in terms of cost-effectiveness. The combination of low maintenance and long-term reliability with geothermal energy and the durability of piezoelectric materials such as quartz reduces ongoing operational costs. However, adding geothermal infrastructure and piezoelectric rigs comes at an initial investment cost and could add to the upfront costs while saving money and increasing efficiency over the long term.

Cost-effectiveness comparison

The economic analysis highlights that the cost efficiency is comparable to traditional renewable energy systems such as solar and wind energy and the proposed hybrid geothermal-piezoelectric energy system. Comparisons regarding materials cost, installation cost, and scalability potential are demonstrated in Table 2 and 3^61,62.

Table 2.

Material costs.

Energy source	Key materials used	Average material cost (USD/kW)
Geothermal-Piezoelectric	Basalt, Granite, Quartz	$800–$1,200
Solar Energy	Silicon Panels	$1,000–$1,500
Wind Energy	Steel, Fiberglass, Rare Earth Metals	$1,200–$1,700

Table 3.

Installation and scalability.

Energy source	Installation cost (USD/kW)	Scalability potential
Geothermal-Piezoelectric	$2,000–$3,000	High, especially in geologically active regions and remote areas
Solar Energy	$2,500–$3,500	Moderate to high, requires large land areas for optimal output
Wind Energy	$3,000–$4,000	Moderate, dependent on wind speed consistency and land availability

• Basalt and granite: Cheap, abundant, and very good in reducing materials costs. An evergreen energy source with good geothermal heat storage capabilities.

• Quartz: Quartz is slightly more expensive because it has piezoelectric properties, but it is still relatively inexpensive compared to high-tech components in wind turbines and solar panels.

• Geothermal-piezoelectric system: Exhibits a competitive advantage in areas with active geothermal fields or seismic movements. The hybrid design enables continuous operation and mitigates the intermittency challenges of solar and wind systems.

• Solar and wind: Despite being effective, both energy sources are limited in their scalability and efficiency in some remote areas, considering both weather dependency and land needed for power generation.

The proposed hybrid system would provide a viable alternative by utilizing sufficient and locally available natural resources such as basalt, granite, and quartz. In particular, if geothermal and seismic activity coincides, it is a cost-effective, highly scalable solution. The hybrid design minimizes intermittency compared to solar and wind systems while keeping lower material and installation costs that cover the way for its large-scale deployment in off-grid regions.

The Findings confirm the superiority of basalt for geothermal energy generation, with better heat retention and conversion efficiency than granite. In piezoelectric energy harvesting, quartz outperforms tourmaline, producing higher voltage and power under mechanical stress, making it more suitable for energy harvesting in seismic and construction environments. The hybrid system shows high power output and efficiency, especially under high heat and stress decisions, integrating geothermal and piezoelectric technologies. This hybrid model is fueling a new era of potentially accessible and cost-effective energy generation, especially in areas capable of geothermal and seismic resources.

Discussion

The discussion analyzes the potential of a hybrid geothermal-piezoelectric energy system. It focuses on system efficiency, scalability, environmental impact, the potential for deployment, and economic consideration toward a low-carbon society. The proposed system’s energy efficiency, low environmental interference, instability, and deployment costs have made it a promising option for off-grid power generation and post-disaster energy rehabilitation.

• System Efficiency and Scalability.

The hybrid geothermal-piezoelectric energy system, thus, outperforms conventional standalone geothermal or piezoelectric systems with a much higher efficiency level. Whereas the former allows for consistent baseload power production due to the continuing use of stones like basalt and granite for heat retention, the latter contributes to the systems’ peak efficiency by generating additional energy by converting mechanical stress and vibration. This results in the combined system having a 70% efficiency at peak performance, which is way higher than geothermal alone. This system is adaptable as the weight and size of the heat-retaining stones and piezoelectric components can be customized according to the energy needs of a particular region, which can be used both for small- and large-scale applications. Moreover, it is cheap because it eliminates the need to develop extensive renewable infrastructure for every geothermal site. It also ensures piezoelectric production integration with existing infrastructure to make the system affordable.

• Environmental Impact.

The hybrid geothermal-piezoelectric energy system has a much lower impact on the environment because it needs large amounts of naturally occurring, abundant stones (like basalt, granite, quartz, and tourmaline), which makes it superior to energy technologies that require rare or processed materials. The system employs these non-toxic, heat-retaining, and piezoelectric materials to disrupt significantly less land than large-scale solar or wind installations and similar resource-hungry infrastructure. In addition, it generates no direct emissions or toxic waste by utilizing geothermal heat and mechanical stress, resulting in slight environmental disturbance. At the same time, due to its low infrastructure requirements and suitability for off-grid application, it can be applied in many geographical environments, including remote areas, which facilitates energy autonomy and diminishes the overall environmental footprint. This results in a highly sustainable energy solution with a significantly lower impact than traditional generation methods and other renewable technologies.

• Feasibility for deployment.

The hybrid geothermal-piezoelectric system can be easily integrated into decentralized and remote regions. The off-grid nature of the product enables it to operate in places with no or little access to conventional energy grids, such as places lacking sufficient sunlight and with poor wind areas and rough landscapes where solar and wind may not work. Producing energy on-site reduces dependence on large electric grids, making it perfect for areas where extending traditional networks would be expensive or impossible. Moreover, the system is integrated with geothermal and piezoelectric energy, enabling it to overcome disaster-sensitive regions and work in extreme conditions while converting seismic oscillations into energy, offering a dependable option for natural disaster areas.

• Economic analysis of stone availability and cost.

Basalt, granite, quartz, and tourmaline are used as the media into which hybrid geothermal-piezoelectric energy systems are constructed and inserted for the results of an economic analysis. Basalt and granite occur almost universally on the earth in volcanic and continental crust areas, meaning they can often be found and delivered cheaply. Quartz is common, occurring as a principal constituent of sand and rock. Although less prevalent, it is mined in specific areas that may impact cost and availability. Basalt and granite are inexpensive because of their abundance and use in the industry. Quartz is cheap, and tourmaline can be more expensive due to limited availability and extraction difficulties. Selecting materials based on regional availability lowers costs and increases system scalability.

The system is upscale and adapts to the energy needs of the area it serves in an economically efficient and ecologically sustainable way. This innovative technology provides an excellent opportunity to promote energy equity in neglected regions, significantly underdeveloped countries, and rural areas.

Technical limitations and challenges

Basalt

• Constraint in Efficiency: Basalt has robust thermal conductivity and thermal insulation. Conversion efficiency was often limited by the slow heat transfer in larger stone volumes, limiting system responsiveness.

• Mechanical Stress: Basalt is highly brittle under certain mechanical conditions, which might impact the lifespan of systems exposed to repeated stress cycles.

• Technical Barriers: Extracting and processing basalt requires intensive energy, which could undo some ecological benefits.

Quartz

• Quartz efficiency constraints: Quartz has excellent piezoelectric properties but has limited efficiency due to low charge generation for minor mechanical stress.

• Material fragility: The crystalline structure of quartz renders it vulnerable to fracturing under no uniform stress, impairing its longevity in long-term or extreme applications.

• Cost and availability: High-purity quartz, needed for efficient piezoelectric energy generation, can be costly and is not geographically evenly distributed.

These limitations emphasize the importance of appropriate material selection, system design optimization, and further studies to overcome scalability and reliability challenges.

Conclusion

This study provides electricity manufacturing by hybrid system to utilize the stone’s geological and piezoelectric properties. The main findings provide high confidence in the feasibility and effectiveness of this approach. Basalt proved to be a better material for retaining heat and converting it into energy than granite. The application of basalt plays a crucial role in geothermal systems, enabling efficient energy extraction from these accessible resources. Quartz produced more electrical output than tourmaline when subjected to mechanical stress, making quartz more piezoelectric efficient in generating electricity. This illuminates its applicability for energy harvesting in seismic or mechanical vibrational environments, including construction sites and earthquake-prone areas. Integration of geothermal and piezoelectric subsystems produced continuous energy output. These adjustments render the system highly efficient and applicable to multiple real-life applications, especially under circumstances that may exert both heat and mechanical stresses at the same time.

The hybrid system has significant advantages over classic ways of renewable energy generators, especially in remote and off-grid areas that have restricted traditional infrastructure access. Renewable energy sources have proven reliable for meeting environmentally friendly, decentralized, and versatile requirements. This provides a solid value proposition in several use cases, but the initial expenditures and relatively high prices for geothermal elements can be challenging in certain regions. This hybrid geothermal-piezoelectric system undergoes continued improvement and optimization that could ultimately become a pillar of the global initiative to build ever more sustainable, stable, and flexible energy sources.

Future scope

Future research will focus on the optimal selection of stone materials and further improve the system design to achieve the highest energy output. This would entail enhanced and more effective testing of various stones exhibiting superior thermal and piezoelectric properties. Scaling the prototype for industrial uses will also be a significant milestone, demonstrating that the hybrid system can provide energy for more extensive commercial operations. Future studies will also conduct a complete life-cycle analysis to evaluate the environmental impacts of the hybrid geothermal–piezoelectric system. This analysis will determine where improvements can be made and ensure that the system continues to be environmentally sustainable. The scope should be expanded to balance the hybrid geothermal-piezoelectric system with other renewable energy sources like wind or solar for a more robust and adaptable sustainable energy generation solution.

Author contributions

Amam Hossain Bagdadee: (Corresponding Author): Conceptualization, Methodology, Data Analysis, Writing – Original Draft, Data Collection, Software, Writing – Review & Editing.Arghya Uthpal Mondal: Writing – Review & Editing.Li Zhang: Validation, Supervision, Writing – Review & Editing.Deshinta Arrova Dewi: Writing – Review & Editing, Supervision.Vijayakumar Varadarajan: Methodology, Writing – Review & Editing.

Data availability

The data supporting this study’s findings are available from the corresponding author upon reasonable request. The data are not publicly available due to privacy, ethical restrictions, and ongoing analysis. For any inquiries regarding access to the full dataset, don’t hesitate to contact the corresponding author at [a.bagdadee@hhu.edu.cn].

Declarations

Competing interests

The authors declare no competing interests.