Low-Enthalpy Geothermal Springs for Power Generation—An Alternative Approach

Abstract

The Earth is under increasing stress owing to carbon emissions. Clean energy forms constitute an area of increasing technological interest. Geothermal energy is a clean alternative energy form that can be harnessed from the Earth's core. The use of geothermal energy resources is gaining substantial interest in many countries, as an integral part of 21 st century clean energy solutions and meeting stringent emission requirements. The objective of this research is to investigate an alternative approach to clean and renewable geothermal energy utilization through geothermal ground water pressure applied within a water turbine. The groundwater pressure from the candidate geothermal sites considered is applied to drive a water turbine for the generation of electrical energy. The geothermal candidate sites are low-temperature (i.e. <60˚C) geothermal springs, where it is not beneficial to apply low temperatures in a Rankine cycle steam turbine due to the low enthalpy. Simple calculations are conducted to estimate the electrical energy output of each candidate site. This may technically be regarded as a thermodynamic problem, albeit one that does not require full thermodynamic cycle analysis. The results of the simple non-rigorous analysis indicate that the electrical energy generation potential is greater when using geothermal water pressure (2.5 MW e ) than when using low geothermal temperature (0.005 MW e ).particularly high projected increase in energy demand. The deployment of alternative and clean energy forms will undoubtedly enhance socio-economic conditions, and over time, climate changes will also be reduced (that is, by preventing anthropogenic greenhouse gases from fossil fuels and the resulting warming).According to World Bank estimates, countries in SSA experience annual electrical power outages ranging from 50 h to 4600 h, which can be juxtaposed with the 8760 h available in a year. As a result, the majority of the populace rely on diesel-or-petrol generated internal combustion engine (ICE) to meet electrical energy needs. However, the cost of using such generators is significant. In the most populous nation in Africa, namely Nigeria, the mean net cost of electrical energy from ICE generators is approximately $14 billion annually, whereas in a smaller nation like Senegal it is approximately $4 million annually. These estimates are also higher than the cost of grid electricity. Also, in Nigeria, the unreliable electricity, costs the economy over $25 billion annually. The broader implications thereof include pollutant emissions that endanger both the environment and human health [1] [2].One of the many means of addressing the electrical energy deficit and improving the environment in developing nations may be through the use of renewable energy forms, such as geothermal energy. Diversifying energy resource generation will enhance energy security and help build an all-encompassing base in the mid-to-long-term energy situation. For example, according to the US Energy Information Administration, as of 2018, car...

Low - medium enthalpy geothermal resource assessment in deep reservoirs of the Llanos Basin - Colombia

“…The climate in Colombia is tropical, with a precipitation volume of 3,400 km 3 /year, of which 2,113 km 3 /year becomes surface runoff. Part of this volume of surface runoff water, approximately 676 km 3 /year (about 4.2 Billion Barrels of Water Per Day -BBWPD), corresponds to the volume of water drained by the river networks of the Llanos Basin [51]. In this basin, the estimated volume of coproduction oil water is greater than 5 BBWPD, due to the regional groundwater flows, which control the formation of hydrocarbon accumulation in the southeastern part of the Llanos Basin [52].…”

“…The evaluation of heat resources was based on the rock volume method, in the Crystalline Basement, Paleozoic sediments, and the Une Formation (see equations for estimating total heat, and their subsequent equations in the methodology section). The definition of the reservoir rock volume in the Crystalline Basement assumed a constant thickness of 1 km for the basin area, resulting in a rock volume of 114,770 km 3 . The heat of rock stored in this volume is 2.13x10 22 Joules, with a mean of 1.86x10 16 Joules.…”

“…The calculated rock volume for the Paleozoic sediments is approximately 38,430 km 3 . This rock volume stores a total of 4.28x10 21 Joules, with a mean value of 3.86x10 16 Joules.…”

“…This increase is driven by the growing popularity of heat pumps using groundwater anywhere in the world [2]. In addition, the energy that can be obtained from geothermal sources is constant, not depending on weather conditions (natural recharge comes from the rainfall), and low CO2 emissions, compared to other renewable energy generation alternatives [3], [4]. The heat extracted during the geothermal power generation process is small compared with the Earth's heat (great portion associated with the radioactive process of elements during their radioactive decay), and the amount of energy is continuously replaced [5], although reservoir pressure is one of the most important parameters involved in geothermal exploitation [6], [7].…”