http://web.stanford.edu/group/efmh/jacobson/Articles/I/JDEnPolicyPt1.pdf

Providing all global energy with wind, water, and solar power, Part I: Technologies, energy resources, quantities and areas of infrastructure, and materials

https://www.geothermal-energy.org/pdf/IGAstandard/WGC/2010/0007.pdf

Direct utilization of geothermal energy 2015 worldwide review

An organic Rankine cycle (ORC) machine is similar to a conventional steam cycle energy conversion system, but uses an organic fluid such as refrigerants and hydrocarbons instead of water. In recent years, research was intensified on this device as it is being progressively adopted as premier technology to convert low-temperature heat resources into power. Available heat resources are: solar energy, geothermal energy, biomass products, surface seawater, and waste heat from various thermal processes. This paper presents existing applications and analyzes their maturity. Binary geothermal and binary biomass CHP are already mature. Provided the interest to recover waste heat rejected by thermal devices and industrial processes continue to grow, and favorable legislative conditions are adopted, waste heat recovery organic Rankine cycle systems in the near future will experience a rapid growth. Solar modular power plants are being intensely investigated at smaller scale for cogeneration applications in buildings but larger plants are also expected in tropical or Sahel regions with constant and low solar radiation intensity. OTEC power plants operating mainly on offshore installations at very low temperature have been advertised as total resource systems and interest on this technology is growing in large isolated islands.

Low­grade heat conversion into power using organic Rankine cycles - A review of various applications

Geothermal energy is the energy contained as heat in the Earth’s interior. This overview describes the internal structure of the Earth together with the heat transfer mechanisms inside mantle and crust. It also shows the location of geothermal fields on specific areas of the Earth. The Earth’s heat flow and geothermal gradient are defined, as well as the types of geothermal fields, the geologic environment of geothermal energy, and the methods of exploration for geothermal resources including drilling and resource assessment. Geothermal energy, as natural steam and hot water, has been exploited for decades to generate electricity, and both in space heating and industrial processes. The geothermal electrical installed capacity in the world is 7974 MWe (year 2000), and the electrical energy generated is 49.3 billion kWh/year, representing 0.3 % of the world total electrical energy which was 15,342 billion kWh in 2000. In developing countries, where total installed electrical power is still low, geothermal energy can play a significant role: in the Philippines 21% of electricity comes from geothermal steam, 20% in El Salvador, 17% in Nicaragua, 10% in Costa Rica and 8% in Kenya. Electricity is produced with an efficiency of 10–17%. The geothermal kWh is generally cost-competitive with conventional sources of energy, in the range 2–10 UScents/kWh, and the geothermal electrical capacity installed in the world (1998) was 1/5 of that from biomass, but comparable with that from wind sources. The thermal capacity in non-electrical uses (greenhouses, aquaculture, district heating, industrial processes) is 15,14 MWt (year 2000). Financial investments in geothermal electrical and non-electrical uses world-wide in the period 1973–1992 were estimated at about US$22,000 million. Present technology makes it possible to control the environmental impact of geothermal exploitation, and an effective and easily implemented policy to encourage geothermal energy development, and the abatement of carbon dioxide emissions would take advantage from the imposition of a carbon tax. The future use of geothermal energy from advanced technologies such as the exploitation of hot dry rock/hot wet rock systems, magma bodies and geopressured reservoirs, is briefly discussed. While the viability of hot dry rock technology has been proven, research and development are still necessary for the other two sources. A brief discussion on training of specialists, geothermal literature, on-line information, and geothermal associations concludes the review.

Geothermal energy technology and current status: an overview

The Global Energy Assessment (GEA) brings together over 300 international researchers to provide an independent, scientifically based, integrated and policy-relevant analysis of current and emerging energy issues and options. It has been peer-reviewed anonymously by an additional 200 international experts. The GEA assesses the major global challenges for sustainable development and their linkages to energy; the technologies and resources available for providing energy services; future energy systems that address the major challenges; and the policies and other measures that are needed to realize transformational change toward sustainable energy futures. The GEA goes beyond existing studies on energy issues by presenting a comprehensive and integrated analysis of energy chalenges, opportunities and strategies, for developing, industrialized and emerging economies. This volume is a invaluable resource for energy specialists and technologists in all sectors (academia, industry and government) as well as policymakers, development economists and practitioners in international organizations and national governments.

Global Energy Assessment: Toward a Sustainable Future

Direct application of geothermal energy : 2005 worldwide review

https://www.geothermalcommunities.eu/assets/elearning/5.7.Geothermalaquaculture.pdf

World-wide direct uses of geothermal energy 2000

Electricity is produced by geothermal in 24 countries, five of which obtain 15-22% of their national electricity production from geothermal energy. Direct application of geothermal energy (for heating, bathing etc.) has been reported by 72 countries. By the end of 2004, the worldwide use of geothermal energy was 57 TWh/yr of electricity and 76 TWh/yr for direct use. Ten developing countries are among the top fifteen countries in geothermal electricity production. Six developing countries are among the top fifteen countries reporting direct use. China is at the top of the latter list. It is considered possible to increase the installed world geothermal electricity capacity from the current 10 GW to 70 GW with present technology, and to 140 GW with enhanced technology. Enhanced Geothermal Systems, which are still at the experimental level, have enormous potential for primary energy recovery using new heatexploitation technology to extract and utilise the Earth’s stored thermal energy. Present investment cost in geothermal power stations is 2-4.5 million euro/MWe, and the generation cost 40-100 euro/MWh. Direct use of geothermal energy for heating is also commercially competitive with conventional energy sources. Scenarios for future development show only a moderate increase in traditional direct use applications of geothermal resources, but an exponential increase is foreseen in the heat pump sector, as geothermal heat pumps can be used for heating and/or cooling in most parts of the world. CO2 emission from geothermal power plants in high-temperature fields is about 120 g/kWh (weighted average of 85% of the world power plant capacity). Geothermal heat pumps driven by fossil fuelled electricity reduce the CO2 emission by at least 50% compared with fossil fuel fired boilers. If the electricity that drives the geothermal heat pump is produced from a renewable energy source like hydropower or geothermal energy the emission savings are up to 100%. The total CO2 emission reduction potential of geothermal heat pumps has been estimated to be 1.2 billion tonnes per year or about 6% of the global emission. The CO2 emission from low-temperature geothermal water is negligible or in the order of 0-1 g CO2/kWh depending on the carbonate content of the water. Geothermal energy is available day and night every day of the year and can thus serve as a supplement to energy sources which are only available intermittently. Renewable energy sources can contribute significantly more to the mitigation of climate change by cooperating than by competing. Likely case scenarios are presented in the paper for electricity production and direct use of geothermal energy, as well as the mitigation potential of geothermal resources 2005-2050. These forecasts need to be elaborated on further during the preparation of the IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation.

The possible role and contribution of geothermal energy to the mitigation of climate change

INTRODUCTION Geothermal (ground-source) heat pumps (GHP) are one of the fastest growing applications of renewable energy (see discussion at the end of this article) in the world, with annual increases of 10% in about 30 countries over the past 10 years. Its main advantage is that it uses normal ground or groundwater temperatures (between about 5 and 30C), which are available in all countries of the world. Most of this growth has occurred in the United States and Europe, though interest is developing in other countries such as Japan and Turkey. The present worldwide installed capacity is estimated at almost 12,000 MWt (thermal) and the annual energy use is about 72,000 TJ (20,000 GWh). The actual number of installed units is around 1,100,000, but the data are incomplete. Table 1 lists the countries with the highest use of GHPs.

/pdf/geothermal-ground-source-heat-pumps-a-world-overview-13rkvhmnni.pdf

John W. Lund

Papers

Direct utilization of geothermal energy 2015 worldwide review

Direct application of geothermal energy : 2005 worldwide review

World-wide direct uses of geothermal energy 2000

The possible role and contribution of geothermal energy to the mitigation of climate change

Geothermal (ground-source) heat pumps a world overview