Your contribution to lower heat bills (and mitigating climate change)

Prof. Leszek Pająk, Mineral and Energy Economy Research Institute, Polish Academy of Sciences

an interview with User4GeoEnergy project representatives

1. Why should municipalities and residents be interested in using geothermal energy in their homes? 

To get the full picture I will divide my answer into two parts. Part one will be more environmen-oriented and part two more technical. Readers can choose what appeals to them more. Both parts are true and equally relevant.

Geothermal energy, especially when exploited in a closed circuit, for example using so-called geothermal doubles, which involves injecting cooled geothermal fluid back into the geothermal reservoir, is a renewable and emission-free source of energy. Recent years have been a period of violent weather phenomena. This draws our attention to the fact that the use of renewable energy sources is not a matter of fashion, but rather priority to fight climate change and economic opportunity, in countries where that is possible. The warming climate, not least due to rising CO2 concentrations in the atmosphere, is a clear fact, which can unfortunately be seen in many ways, like rising temperatures, more weather extremes like storms, rain, droughts, forest fires, etc. around the globe. The question is:  will it still be possible to reverse the processes that are taking place to stay within the 1.5°C temperature increase? Renewable energy, e.g. geothermal, is a powerful tool to fight against global warming and also economic opportunity for savings by harnessisng local resources and a way to improve quality of life. 

2. Can heat from combined heat and power plants (CHP)  be used more efficintly?

Technically speaking, the User4GeoEnergy project could just as well be called User4EffectiveHeatUtilisation. Why? The answer to this question is quite simple. The proposed solutions aim at improving the efficiency of energy use, regardless of its origin. Energy and its efficient use are subject to the same laws of nature, regardless of its origin. Renewable energy has only a moderate or zero environmental impact when it is transformed from its original form into a form that can be managed by the user. As the User4GeoEnergy project focuses on the use of geothermal energy for heating purposes, my discussion will focus on this topic. 

Conventional power plants, using water as a working medium in the evaporator (boiler) – turbine – condenser system, work the more effectively the greater the pressure difference between the turbine inlet and outlet. The condensation of steam at the turbine outlet takes place in special exchangers called condensers. Water is transformed therem from vapour to liquid, accompanied by a significant drop in pressure. For condensation to take place, a constant source of cooling is needed. The temperature at which condensation usually occurs in condensers is in the order of 50-60°C. This allows the condensation of water vapour at a pressure lower than 0.2 atm, i.e. there is negative pressure in the condenser compared to atmospheric pressure. If the pressure in the condenser was 1 atm, the water vapour would condense there at 100°C. When talking about use of waste heat from condensation, we would have to be able to handle energy resources with temperatures below 60°C. Only then could we talk about waste energy – otherwise not. Why? 

Using energy with temperatures above 60°C for heating purposes means depleting electricity production and using very valuable energy, not waste energy. Why?

Because we can still produce electricity from steam, which has a temperature typical for the supply temperature of district heating systems, i.e. around 110°C, by cooling it down to around 60°C. This is therefore not a waste of energy. This is where the User4GeoEnergy project ties in with conventional energy. With geothermal energy, it is the same. We also want to use the lowest possible temperatures that characterise the energy resources used. This allows them to be used efficiently and in clean way. In addition, the power of a single geothermal borehole increases as we can obtain more energy from each m3 of extracted water. One can therefore say that a consumer good for geothermal energy will also be an ideal consumer of waste energy from conventional installations. Reducing the requirements for the supply and return temperature of the energy carrier makes it possible to obtain geothermal heat without the need for additional, so-called peak energy sources. This, in turn, significantly increases the availability of geothermal resources. The availability of low-temperature geothermal resources is wider than that of high-temperature. It is therefore difficult to speak of a conflict of interests, but one can safely speak of the common interest of both geothermal resources and conventional energy carriers. Interestingly, this conclusion also applies to solar energy, biomass and, in particular, heat pumps and condensing boilers.

Of course, many smaller towns do not have combined heat and power (CHP) plants, so local heating plants fired by fossil fuels have been and continue to be built, polluting the environment. At the same time, many of these places have geothermal resources with temperatures of 60-90°C. Reducing the supply temperature in district heating systems makes it possible to use not only geothermal energy but any other energy carrier efficiently.

3. What solutions do you propose in the User4GeoEnergy project?

In the User4GeoEnergy project, we want to popularize the use of low-temperature heating systems, for which the required supply and return temperatures of the energy carrier are as low as possible. In practice, this means supply temperatures of 40°C and return temperatures of 30°C. This imposes the use of large-area heating, supported for example by air heating. Please keep in mind that if you want to maintain the so-called thermal comfort conditions, i.e. approx. 20-22°C, in residential or commercial spaces, heat carrier temperatures of approx. 30°C are quite feasible.

4. Why is it so important to lower the requirements for the heat source and the distribution system?

There are many reasons. Lower temperature requirements for the source by the heating system means lower energy losses in transmission pipelines and no or a significant reduction in the need for peak boilers. If we decide to use a peak source anyway, lowering the temperature requirements will increase the efficiency of its operation. This is of paramount importance, especially in the case of heat pumps and condensing boilers. The Le Chatelier’s principle, well known in physics, perfectly explains why it is important to lower the requirements for a heat source. It explains the fact that any deviation from the equilibrium, as described by the ambient conditions, costs more the bigger the deviation you want to achieve. This principle can also be applied to a situation in which the higher the temperature of the heat carrier we want, the more it will cost us. This cost is the consumption of the energy carrier. For those readers who have a broader knowledge of physics, this formulation may resemble the Second Law of Thermodynamics.

The most efficient way, from an energy point of view, is therefore to heat with as low a temperature as possible. Of course, in addition to technical effects, the laws of economics are equally important in everyday life. Contrary to the laws of nature, however, economics can change. After all, concept of profitability depends on a reference point that is not constant over time. It is worth paying attention to the recent rapid increase in the prices of energy carriers. What was not profitable three years ago, may become quite attractive in the future. 

5. What technical changes to buildings does this involve?

The changes the project focuses on generally aim to increase the heat transfer surface area of heating installations.  
An increase in the heat transfer surface area means that the temperature of the energy carrier can be lowered. These changes do not in any way mean giving up on the thermal comfort. On the contrary, the proposed solutions can significantly improve these conditions. It is a well-known fact that the temperature profile when using floor heating is closer to the so-called ideal profile.

6. Is it worthwhile? Who is already using such solutions?

The profitability of the proposed solutions can be considered in at least three areas: economic, energy and environmental. As far as energy is concerned, of course, such solutions are profitable, as they make it possible to reduce energy losses and lower the consumption of conventional energy carriers while maintaining the comfort of buildings. The energy effects are easily followed by environmental effects. Lower consumption of fossil fuels means lower emissions.

Economic profitability can arouse the most emotions. This is always a question of individual solutions and the benchmark used. It is also extremely important to indicate what we will gain. If even the economic assessment will show a loss? Perhaps at that cost, we will achieve something worth paying for, such as comfort and a clean environment. Does everything we do always have to pay off? In everyday life we do many things that do not bring an economic return, e.g. comparing the cost of buying a car with the cost of using public transport would probably encourage people to take the bus or tram to work. Why do some of us drive? It is not worth it!

The proposed solutions are widely used by individual consumers who use heat pumps daily. These solutions bring beneficial effects and are willingly used by consumers using condensing boilers.

7. How can district heating companies encourage onsumers to make such changes?

District heating companies can encourage consumers to apply certain solutions, e.g. by making the price of the heat sold dependent on temperature requirements of consumers. The use of discounts, associated with deep cooling of the energy carrier, can foster the development and dissemination of the solutions proposed here.

8. If all this seems so obvious, why are these solutions not yet widely used?

There are many answers to this question, and in my opinion, the three most feasible are following:

  • For a district heating company, installing a peak source which matches the heat source to the customer’s installation, is much easier than encouraging the customer to match his installation to the capabilities of the source,
  • The installation of a peak source is an eligible cost, allowing it to be included in the price of the energy sold to the customer. After all, the energy supplied by the heating company is ultimately paid by the consumer anyway. A technically easier and quicker solution, transferring the final cost of covering heat needs to the consumer, causes a lack of motivation for this type of action.
  • Controlling power in a system where the temperature of the energy carrier exceeds the needs of the consumer is much easier.

9. What experience can partners from Iceland and Norway provide in this area?

The choice of partner countries is not accidental. Both countries have long and rich experience directly or indirectly related to use of geothermal energy and energy efficiency. 

Iceland is the European leader in the use of geothermal energy. Of course, its resources are unique in terms of parameters. Although not all of Iceland’s experience can be easily transposed to other European countries, including Poland, Slovakia and Hungary, it is nevertheless worth taking advantage of what can certainly be transposed. 

I think the broader approach to geothermal resources as something more than just a source of energy is worth following. Geothermal fluid can be used in many ways. Its properties can drive other business sectors, such as organic plants and animal husbandry, the cosmetics industry, tourism, algae cultivation, innovation, resources parks etc. Some of these applications of geothermal energy can also be found in other European countries. Iceland uses it on a large scale in many places.

It is also beyond dispute that the economic savings from using geothermal instead of oil, are substantial in Iceland and have had positive impact on the currency account and contributed significantly to Iceland’s prosperity, especially in times of need. The annual savings have been on average of 2,9% of GDP 1970-2018, which is on average equivalent to annual military spending in average military nations.   

As for Norway, it is the world leader in energy-saving and energy efficiency. Many innovative solutions related to energy-efficiency are widely used there in the construction sector. Also noteworthy is the experience in developing heat pump technology. Most of the Norwegian experience is therefore focused on the use of low-temperature heating systems, which is directly related to main objectives of the User4GeoEnergy project.

10. To what extent does the use of geothermal energy for district heating contribute to mitigating climate change?

With its negligible CO2 emissions, renewable energy, like geothermal, is a great tool to fight against global warming while other forms of energy, e.g. oil and gas, have significant CO2 missions.  In Iceland, yearly CO2 savings using geothermal heat were equivalent to 0.4 kg/kWh in 2018, compared to if oil would be used. 

Convincing anyone to use geothermal energy seems unnecessary from the utility point of view. Geothermal energy, despite its disadvantages, has undoubted advantages over other RES sources, not to mention conventional sources. Its resources are not dependent on weather conditions. The temperature and capacity are almost invariable over time. This makes it a reliable and clean energy carrier.

11. Where to find more information on these solutions?

I encourage you to visit the project website and to study literature and websites dedicated to low-temperature heating or heat pumps. Many of the technological solutions proposed there fit perfectly to the framework of our project and energy efficiency in a broader sense. Please remember that the suggested solutions will also work perfectly with conventional energy carriers, without exception.

In the cover image Prof. Leszek Pająk – the manager of the User4GeoEnergy project who answered most of questions above.


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