Finally the Special Report on Renewable Energy (SRREN) sources and Climate Change mitigation (Final Release) was released in May 2011 by IPCC. This report gives the status of Wind, Solar, Geothermal and other renewables in the context of ongoing debate on carbon dioxide emissions, climate change and future plan of action for all the countries, especially for those countries under non-OECD. ighlights of the report related to geothermal energy are as follows:
The available heat that can be extracted from the depth of 3 km in the earth is 34 x 106 EJ. Theoretically an amount of 146 EJ/Y of electric power can be generated from this energy. Technology for generating electric power from hydrothermal sources is very matured and is in place for the last 100 years or more and at present over 11,000 MWe being generated across the countries. Ground heat sources technology to cool or heat space is also very well developed and in some countries it is mandatory to use ground source heat pumps to cool or heat residential space and districts. The status of electricity generated and direct application through geothermal is regularly updated during the world geothermal congress held every five years. With regard to direct application, during 2009 63% geothermal energy was used for space heating of buildings, 25% for balneology, 5% for greenhouse cultivation, 3% for dehydration, 3% for fish farming and 1% for snow melting.
For geothermal to reach its full capacity in climate change mitigation, it is necessary to overcome technical and non-technical barriers. These barriers can be overcome by making amendments in renewable energy policies. Geothermal resources are either site specific (hydrothermal sources) or site independent (EGS and GHPs). The distance between electricity markets and sources becomes a significant factor in the economics of power generation and direct use. These are technical barriers. Non-technical barrier include lack of information and awareness related to geothermal energy resources among the public. This can be overcome by disseminating information through a variety of media and also holding seminars and symposia. Institutional barriers include lack of specific laws governing geothermal resources. In many countries geothermal resources are considered as mining or water resources.
Policies should be clear regarding the use of GHPs. For example, heating/cooling individual domestic homes does not need any specific policy but implementation of district heating system requires  different policy framework. Policies that support R and D programmes would benefit geothermal technologies, especially emerging technologies like EGS. Fiscal incentive, public finance for research and demonstration, subsidies, guarantees, tax write-offs to cover commercial upfront exploration costs, including high risk drilling costs are a few issues that a policy should address to encourage geothermal resources. Equally important is the feed in tariff that needs to be attractive for the investors. Experience with the countries that are successful in the development of geothermal energy for power generation and for direct applications shows that such developments are closely linked to the government policies, regulations, incentives and initiatives.
Geothermal energy resources are independent of weather conditions of any region, provides base-load electricity, reduces GHG emissions and provides solutions for Clean Development Mechanism (CDM). Geothermal energy sources can generate substantial carbon credits under CER. For example the Darajat III geothermal power plant of Indonesia, established in 2007 has so far generated 650000 carbon credits per year thereby reducing the life cycle cost of geothermal energy by about 2 to 4%. This is a substantial amount! Geothermal energy does not pose any environmental problems. The GHGs that are emitted by geothermal power plants is very small and such gases any how would have escaped into the atmosphere through natural vents eventually. In the case of EGS supported power plants, the GHG emissions are nil. Electric power enerated from geothermal power plants can easily be integrated to any type of grid or can also be developed as stand-alone systems especially in remote villages. Since the geothermal power plants provide base load power, scaling up the old power plants or integrating new ones with the old ones is not a major issue.
Drilling of production and injection of geothermal wells have a success rate of 60 to 90% and the cost of wells depends on permeability, porosity, depth of drilling, temperature of the reservoir, availability of drilling rigs, composition of the fluids etc. These factors take 20 to 35 % of total investment. Geothermal projects in general, are financed in two different ways with different return rates. One is on equity basis and the other on debt basis. Equity rates are generally higher than the debt rates. The capital structure of geothermal-power projects are  commonly composed of 55 to 70% debt and 30 to 45% equity, but in some countries like the USA, debt lenders usually require 25% of the resource capacity to be proven before lending money. Operation and maintenance costs include variable and fixed costs that are directly related to the power generated from a geothermal power plant. It is necessary, over a period time, to drill new wells to maintain the fluid/steam flow rate. These are make-up wells and they will add to the cost of the project..
Land requirements for geothermal power plants are very small. By designing proper surface installation systems ( pipes, roads, steam/fluid separators, drilling pads, power stations) and adopting directional drilling techniques, the land area above the geothermal resources site can be developed for other purposes such as farming, horticulture, forestry etc. as has been developed at Mokai and Rotokawa in New Zealand and national park in Olkaria geothermal site in Kenya.  Land requirement, for example, for a 110 MWe geothermal flash plant is 1260 m2/MWe and for a 20 MWe binary plant is 1415 m2/MWe. The electricity output is substantial. For example 20 MWe binary power plant installed in an area of 1415m2/MWe would generate 170 GWh/yr.
The IPCC Fourth Assessment Report (AR4) estimated a potential contribution of geothermal to world electricity supply by 2030 of 633 TWh/yr (2.28 EJ/yr). Climate policy is likely to be one of the main driving factors of future geothermal development, and under the most favourable policy of CO2 emissions (<440 ppm) geothermal deployment by 2020, 2030 and 2050 could be higher by several factors.
In a nutshell, the geothermal-electricity market appears to be accelerating as seen from the increase in the installed and planned generation capacity. Gradual introduction of new technologies like the EGS is expected to enhance the power production to 160 GWe by 2050. Power generation with binary plants permits the possibility of producing electricity in countries that have no high-temperature resources. Investigations are on in using CO2 as a working fluid in EGS based power projects. COÂ2 has more efficient than water in extracting heat from the underground reservoirs. This would provide means to sequester COÂ2 and the same time generating energy with low carbon emission.
Oil fields can also be used to extract geothermal energy. Abandoned oil and gas wells capable of supplying temperatures higher than 120º C. The advantage here is lowering of project cost due to availability of drilled wells. The only cost involved here is cleaning the wells.