Low-enthalpy Geothermal Sources Research Articles

Low enthalpy geothermal source for sustainable energy production in small islands: a real case study

The global demand for clean and sustainable energy sources has significantly increased in recent years, mainly because of concerns about climate change and the finite nature of traditional fossil fuel reserves. In this context, geothermal energy has gained significant attention as a reliable and eco-friendly alternative. In particular, low enthalpy geothermal resources have emerged as an attractive option due to their accessibility, widespread distribution, and potential for decentralization. Moreover, reliability and flexibility of this source allow for year-round utilization to meet diverse energy demands, resulting in reduced dependency on traditional energy sources and associated greenhouse gas emissions. For this reason, geothermal energy appears to be a promising solution in small islands, where energy production is often a challenge due to the absence of infrastructures that make them energy-dependent on the mainland. Therefore, in this work, low enthalpy geothermal source is considered as effective and sustainable solution for electrical energy production in small islands. As case study a low temperature source available in Ischia island, Southern Italy, is considered. The proposed solution is analysed from energy, economic and environmental point of view.

Assessment of geothermal energy use with thermoelectric generator for hydrogen production

In this work, a new model for producing hydrogen from a low enthalpy geothermal source was presented. Thermal energy from geothermal sources can be converted into electric power by using thermoelectric modules instead of Organic Rankine Cycle (ORC) machines, especially for low geothermal temperatures. This electrical energy uses the water electrolysis process to produce hydrogen. Simulation and experiments for the thermoelectric module in this system were undertaken to assess the efficiency of these models. TRNSYS software is used to simulate the system in Hammam Righa spa, the temperature of this spring is 70 °C. Obtained results reveal that in hammam righa spa in Algeria, 0.5652 Kg hydrogen per square meter of thermoelectric generator (TEG) can be produced in one year.

Trigeneration system driven by the geothermal and solar sources

In this study, a novel trigeneration system is conceived to produce heat and electricity and to provide cooling for the health treatments and touristic facilities of a spa, based on the natural hot water and solar sources. The power generation components, individually considered, are commercially available ones, but their novel combination and the complex power flow management represented a challenge. The proposed system is composed of a low-temperature driven adsorption chiller, thermally activated by a low enthalpy geothermal source, and by hybrid photovoltaic/thermal panels. In this way, multiple objectives are achieved: produce electricity and thermal energy by renewable sources; optimise the use of different renewable sources (geothermal and solar); use the energy available for free from a geothermal source also during summer (otherwise wasted) to produce a cooling effect, and in so doing, avoiding the huge electricity consumption of conventional air conditioning units in summer; reduce the temperature of the fluids released to the environment (in a natural reserve); reduce the CO2 emissions by 45% with respect to the present configuration, limiting the global warming. The mathematical models were experimentally validated using a pilot plant built on purpose, and the performance of the whole system was analysed and discussed.

Energy Performance of a Kalina Cycle based CHP plant driven by low-enthalpy geothermal sources

The low-enthalpy geothermal sources can be efficiently exploited for heat and power cogeneration by using the KCS-34 Kalina cycle systems. The maximum power for given heat source temperature and cooling temperature is obtained for a certain value of the ammonia-water solution concentration and turbine exit pressure. The Cycle-Tempo simulation software is a very useful tool to investigate variation of some cycle parameters in order to obtain the maximum energy efficiency. In this paper the performance of a KCS-34 Kalina cycle based CHP plant is investigated to exploit a geothermal source with 120°C temperature present in North-West of Romania. It was found that by using the heat and power cogeneration the energy efficiency can be increased from 16.76% to 57.86% in winter and to 33.44% in summer.

Thermodynamic Analysis of a Half-Effect Absorption Cooling System Powered by a Low-Enthalpy Geothermal Source

A thermodynamic analysis of a half-effect absorption cooling system powered by a low-enthalpy geothermal source was carried out. This paper presents modeling of the half-effect absorption cooling system operating with an ammonia/lithium nitrate mixture and based on the first and second laws of thermodynamics, using as energy inputs real data from two geothermal wells located at Las Tres Vírgenes volcanic complex, Baja California Sur, México. Plots of coefficients of performance and exergy efficiency against condenser, evaporator, and generator temperatures are presented for the half-effect cooling system. The results showed that the system was able to operate at generation temperatures between 56 and 70 °C, which were supplied by the geothermal wells in order to produce cooling at temperatures as low as −16 °C, achieving coefficients of performance between 0.10 and 0.36, while the exergy efficiency varied from 0.15 to 0.40 depending on the system operating temperatures.

Exergy: Game Changer or Game Maker

Many standard practices of today in the High Performance and Sustainably Green Buildings simply rely on the First-Law of Thermodynamics and economic feasibility in their evaluation and ratings. Although these practices seem to be quite `efficient` and green, new metrics, which are based on the Second-Law, namely exergy rationality metrics show that these practices are not feasible and environmentally advantageous, unless they are redesigned accordingly. For example, a simple ORC system using low-enthalpy geothermal source is not feasible, which means that such a system may save money and apparently energy but definitely destroys exergy compared to direct use of the thermal power from the geothermal well. This poster emphasizes the urgency of switching to exergy-based designs and practices.

Geothermal resources and reserves in Indonesia: an updated revision

<p><strong>Abstract.</strong> More than 300 high- to low-enthalpy geothermal sources have been identified throughout Indonesia. From the early 1980s until the late 1990s, the geothermal potential for power production in Indonesia was estimated to be about 20 000 MWe. The most recent estimate exceeds 29 000 MWe derived from the 300 sites (Geological Agency, December 2013). <br><br> This resource estimate has been obtained by adding all of the estimated geothermal potential resources and reserves classified as "speculative", "hypothetical", "possible", "probable", and "proven" from all sites where such information is available. However, this approach to estimating the geothermal potential is flawed because it includes double counting of some reserve estimates as resource estimates, thus giving an inflated figure for the total national geothermal potential. <br><br> This paper describes an updated revision of the geothermal resource estimate in Indonesia using a more realistic methodology. The methodology proposes that the preliminary "Speculative Resource" category should cover the full potential of a geothermal area and form the base reference figure for the resource of the area. Further investigation of this resource may improve the level of confidence of the category of reserves but will not necessarily increase the figure of the "preliminary resource estimate" as a whole, unless the result of the investigation is higher. A previous paper (Fauzi, 2013a, b) redefined and revised the geothermal resource estimate for Indonesia. The methodology, adopted from Fauzi (2013a, b), will be fully described in this paper. As a result of using the revised methodology, the potential geothermal resources and reserves for Indonesia are estimated to be about 24 000 MWe, some 5000 MWe less than the 2013 national estimate.</p>

Can you take the heat? – Geothermal energy in mining

In 2013, there are less than 20 documented examples of operational geothermal systems on mine sites worldwide. This is surprising, since on remote mine sites, where fuels may have to be shipped in over great distances, heating and cooling from low-enthalpy geothermal sources may have a significant advantage in operational cost over conventional energy sources.A review of factors affecting the feasibility of geothermal systems on mining projects has been undertaken, and has identified the possible configurations of geothermal systems suitable for the exploration, operational and closure phases of mine development. The geothermal opportunities associated with abandoned or legacy mines are also discussed. The potential categories of heat reservoirs associated with mine sites are: natural ground; backfilled workings; mine waste; dewatering pumping; and flooded workings/pit lakes.The potentially lower operational costs for heating and cooling must be offset against the capital cost of a geothermal system. The focus for mine operators should therefore be on identifying at feasibility stage those projects where conditions are favourable for geothermal systems, the potential risks are understood, the economics are likely to be beneficial, and geothermal systems can be established while minimising additional capital costs.

Environmental and thermal benefits of linking Brayton, absorption chiller, and organic Rankine cycles with low-enthalpy geothermal source at an arid-zone area of Libya

A combined system which consists of Brayton, LiBr/H2O absorption chiller, and HFC 245fa organic Rankine cycles has been developed and linked to a high potential low-temperature geothermal source of energy. Situated in an arid-zone area at Waddan City Libya, the geothermal source could provide sufficient energy for the City and surrounding villages and satisfy their full electrical demand of 100 MW in an uninterrupted and stable way. The system could also supply district heating and hot water. The simulated results show that the output power and thermal efficiency of the combined cycles were improved by 5 per cent and 1.5 per cent, respectively, compared to a standalone gas turbine and it also reduced carbon emissions by 55.7 per cent (291 g/kWh instead of 649 g/kWh). Incorporating district heating to the electrical energy raised the energy utilization factor to 55.1 per cent.

Low Enthalpy Geothermal Energy for Greenhouse Heating at Nea Kessani Xanthi, Greece

This article deals with the direct use of a low enthalpy geothermal energy source situated in Northern Greece (Potamia-Nea Kessani) to heat a greenhouse where vegetables (such as tomatoes) could be grown. A description of the geothermal field in Potamia-Nea Kessani is given together with the technical characteristics of the developed greenhouse and the heating installation. A technoeconomic analysis of two different greenhouse-heating approaches is given and the simple payback period is calculated. It was found that in Nothern Greece there are many areas (such as the one described in this article) where low enthalpy geothermal sources could be exploited easily at a very reasonable cost.

Greenhouse heating using geothermal energy

This paper describes the use of a low enthalpy geothermal source in Northern Greece to heat a greenhouse where flowers could be grown, especially roses. The different parts of the developed greenhouse, the heat loss calculation and the heating system are described. An analysis is given of different greenhouse heating approaches, and a description of the selection procedure, following low-cost and high-efficiency criteria. An analysis is also made of an extended heating system, which uses low temperature water or direct geothermal fluid to heat a second greenhouse similar to the first. The second greenhouse could be used for strawberry cultivation, where an inside temperature of 15°C is required. The existing greenhouse, described in this paper, proved to be very important and beneficial for this area of Northern Greece, with its numerous low enthalpy geothermal sources.