Light in the well: new plants will extract energy from the underground "hot ocean"

Scientists have developed a scheme for a hydrothermal power plant that can generate electricity at coolant temperatures from 60 °C. The existing analogs can function only at a coolant temperature above 100 °C. The development will make it possible to use underground water heated by the planet's internal heat as an energy source. Apart from Western Siberia, Kamchatka, Sakhalin, the Kurils and the North Caucasus are promising for the introduction of such technologies. More details about the possibilities of new geothermal stations - in the material of "Izvestia".

How to get energy from sources with low temperature

Researchers from Tomsk Polytechnic University have created and tested a prototype thermal power plant, which will help develop the resources of the underground "hot ocean" - the waters that are contained in the bowels of the earth, heated by the internal heat of the planet. This includes underground reservoirs, which are concentrated in Western Siberia.

The proposed development is based on binary-type thermal power plants. In such systems, an intermediate coolant with a low boiling point is used as a transition link. This makes it possible to use relatively non-hot energy sources.

- As a working body in the system we proposed ozone-safe gas R245fa from the group of freons. This substance can boil at 47 °C. Its application will allow to use sources with temperature of about 60-70 °С. This is enough to produce electricity of the required parameters with the help of our proposed scheme," said the project manager Stanislav Yankovsky, associate professor at the TPU Butakov Research and Education Center.

He explained that the station consists of several modules: heater unit, evaporator, condenser, screw detander and generator. In addition, it is equipped with the necessary measuring equipment and control system. Among other things, the possibility of remote control of the station has been developed.

In general terms, the scientist reported, the production process looks as follows. Fluid from a geothermal source is lifted from the well to the surface under pressure. Then, through a heat exchanger, the fluid gives heat to the refrigerant. It, boiling, transfers energy to a screw detander, a device that converts the internal energy of the gas into mechanical energy.

On the shaft of the detander, Stanislav Yankovsky added, a generator is installed, which, in turn, generates electricity. At the same time, the spent refrigerant is condensed, after which it is used in the next cycle of thermal transfer. In parallel, the heat obtained from underground water, if its temperature is sufficient, can be used for heating consumers or for hot water supply.

As emphasized by the scientist, at present, an experimental pilot plant with a capacity of 25 KW has been constructed on the territory of TPU according to the proposed scheme. With its help, engineers have worked out the modes of energy generation on a model thermal well.

As a result, the researchers determined the minimum temperature of groundwater extracted to the surface, at which the coefficient of efficiency of the geothermal power plant will be positive. This is about 60 degrees Celsius. Existing analogs can only function at temperatures above 100 degrees Celsius.

How GeoPPs will allow to develop remote areas

In the future, Stanislav Yankovsky shared that based on the proposed scheme, geothermal power plants can be built in series for remote, isolated from the grid infrastructure settlements and industrial facilities. This will make it possible to do without expensive importation of energy resources (coal, fuel oil, etc.), i.e. to use local underground sources.

- TPU scientists have developed a map of the most promising Russian territories for geothermal energy. They include Kamchatka, Sakhalin, Kurils, North Caucasus, and Western Siberia," said Gleb Shishaev, an engineer at TPU's Heriot-Watt Center, a participant in the project.

Photo: TASS/Strunin Anatoly

He added that when building the map, specialists took into account the density of geothermal resources, the depth of their occurrence, as well as population density, remoteness of territories from the infrastructure and the current cost of electricity.

According to the project participants, the implementation of the scientists' development will make it possible to create autonomous GeoPPs in remote communities and reduce the cost of electricity by three or more times compared to diesel power plants.

- Today in Russia, about 74 megawatts of electric energy are generated with the help of GeoPPs, which puts Russia on the 19th place among 64 countries that use this resource. This is strange because there are significant geothermal anomalies on the territory of our country, which can become the basis for the development of this type of energy," Professor Mikhail Khutorskaya, head of the Heat and Mass Transfer Laboratory of the Geological Institute of the Russian Academy of Sciences, told Izvestia.

Photo: TASS/Strunin Anatoly

He said that, for example, on the border of the Kaliningrad region and Lithuania there is a geothermal anomaly, where local residents use hot water from wells for household needs, but it is not used to generate electricity. At the same time, in neighboring Lithuania, a geothermal power plant operates on the basis of the same underground reservoir.

According to Mikhail Khutorsky, modern drilling technologies make it possible to reach the depths necessary for the extraction of high-temperature resources. Their development will reduce dependence on fossil energy sources, improve the environment and increase energy security.

Geothermal energy is one of the most promising areas in the field of renewable energy. It is based on the utilization of heat that lies beneath the surface of the earth. It is especially relevant for countries with cold climates. In Russia, where large areas are occupied by northern and hard-to-reach regions, geothermal energy can play a key role in ensuring energy independence, shared Professor of the Department of Thermal Power Plants of Novosibirsk State Technical University and Advisor to the Director of the Institute of Thermophysics named after S.S. Kutatelad. S.S. Kutateladze Institute of Thermal Physics of the Siberian Branch of the Russian Academy of Sciences, Sergey Elistratov.

Photo: RIA Novosti/Alexander Piragis

He reminded that the world's first binary-type geo-electric power plant was developed in our country. Such a station was launched in Kamchatka in the 1960s. It operated on sources with a temperature of about 80 °C. Its capacity was about 600 kW. However, later the emphasis was placed on the use of hydrocarbons. As a result, the leading position in geothermal energy was lost, and now we are in a catching-up position in relation to a number of countries that are actively developing these technologies. Nevertheless, thanks to the existing reserve we can make up for lost time, the scientist expressed hope.

According to him, one of the promising areas is the generation of electricity from water that is squeezed out of underground formations during oil production. Its temperature in this case is close to 100 degrees. Therefore, oil producers are interested in developing the technology proposed by Tomsk engineers.