Renewable sources of energy at home – is this cost-effective? (scientific blog)

A wind farm in Kopań near Darłowo

A measurement installation with elements of an Off-grid photovoltaic system in Miękinia

A boiler room with heat pumps at the Laboratory in Miękinia

A reason to write this article was the last hot summer, one of the hottest summers for a number of decades. If someone did not believe that global warming was a fact and thought it was just an ecologists’ way to threaten people, after the recent heat wave they can get rid of any doubts. And if we have to bear tropical temperatures, we need to try to turn them somehow to our advantage. 


How to do it? One answer are solar energy collectors and photovoltaic panels, but are they cost-effective? Or maybe renewable energy sources, which we are going to talk about in this article, are our future and a necessity that follows from diminishing energy sources? Surely yes. But in order to encourage people to invest in renewable sources of energy, something else is needed apart from appealing to the responsibility for the future of our planet and mankind, a positive economic calculation is also required. About renewable sources of energy I am talking to the scientists of the Department of Fossil Fuels at the Faculty of Geology, Geophysics and Environmental Protection – professor Wojciech Górecki and Wojciech Luboń, MSc.  


Ilona Trębacz

Prosumer – who is it? 


In 2030, 20 per cent of energy used in the countries of the European Union is supposed to be obtained from renewable sources of energy. Why is energy obtained from renewable sources so important?   

W. Górecki: It is important because it has a huge impact on the protection of the natural environment, especially in the sector of power engineering, as the emission of greenhouse gases is minimal, and in case of, for example, geothermal energy, it is in fact close to zero. Because of that, it is worthwhile to invest in this area. However, it needs to be stated clearly that Poland’s conditions for the effective use of renewable sources of energy are average. In general, in our country, this kind of energy is of local character. There are areas where we can use solar, wind and geothermal energy very effectively and economically. But there are other areas where economically it is not cost-effective. Because of that, Poland will have to get involved very seriously in research into technologies connected with renewable energy sources and take advantage of world achievements in this field, so that in 2030 it could produce 20 per cent of energy from renewable sources. It is a great challenge.   


How much energy from renewable sources does Poland currently produce?
W. Górecki: It is difficult to estimate, but it is said to be about 6.5 per cent. It all depends whether we count in these estimates wood combusted in power stations. In such calculations, heat obtained from renewable sources of energy is not taken into account, that is, for example, heat produced by solar energy collectors, which are more and more often found on private houses and public buildings such as hospitals. Energy from renewable sources has to be used rationally and to the extent that is needed. It does not make much sense to put solar collectors everywhere, since the entire energy produced by them cannot be used. An example here can be schools during summer holidays – at the time where most energy is produced, schools are closed.  


In our country, taking climate into account, do we at all have a possibility to increase significantly the production of energy from renewable sources? 
W. Luboń: As far as solar energy is concerned, the conditions and insolation in Poland are practically the same as in, for example, Germany, where this sector of power engineering has developed really incredibly. In our country, it is only in the phase of development. Our problem are not climatic conditions, but the financial support of the state and a lack of suitable governmental regulations. In my opinion, the use of solar energy in Poland has a good chance for development, an example of which – at the same climatic conditions – are our Western neighbours. 
W. Górecki: There is a great future for distributed generation, that is distributed energy produced by people in detached houses and larger public buildings. It can be very effective, especially now when a new law concerning renewable sources of energy has been adopted, which is in favour of micro power systems. This does not apply only to solar energy, but also to wind, water and geothermal power.  


From which sources can we produce energy most effectively then? 
W. Górecki: It all depend where we are. There are, for example, wind distribution maps on the basis of which we know what are the best locations for wind farms. On the basis of geological surveys we know where we have the best chance for the production of geothermal energy. We know places in our country which have the biggest numbers of sunny days. All the information needs to be taken into account when we want to invest in renewable sources of energy.   


Should we therefore encourage Polish people to install energy production systems in detached houses? Will photovoltaic panels prove effective in case of a single-family household? 
W. Górecki: There is a great need to convince people to purchase micro-systems of renewable energy sources. The society has limited knowledge in this field, hence education concerning renewable sources of energy should be two-way. On the one hand, it should be provided in schools, because if a child acquires sufficient knowledge regarding renewable energy sources, as an adult, while planning the building of their own house, still at the design phase, they will consider having their own micro power system, which will be much cheaper than changing the system in an already existing house. On the other hand, there should be organised workshops aimed at citizens, local governments, owners of construction companies, or roofers, who will be able to find out that it is economically worthwhile to design such a system, and how it should be done effectively. Education in this field has been taking place for some time in Germany, where it has already brought some measurable benefits. For example, people are taught how to construct a roof, where solar and/or photovoltaic panels should be places, how much it will all cost, and when it will pay back. We just want to do a very similar thing in Miękinia; we are planning to visit schools with lectures concerning renewable sources of energy, but we also want to organise training sessions for local authorities and potential investors who are interested in the idea.  


Could you explain the process of energy production for a household? 
W. Luboń: For some time now we have used the name prosumer, which means both a producer and a consumer of energy. When I install a 3kW system – as it is stated in the new act of renewable energy sources – the energy produced by my photovoltaic system can be used directly by me, or transferred into the electricity grid. According to the agreement with an electricity distribution company, the prosumer’s meter is exchanged to a bidirectional one, thanks to which it is possible to see both energy produced and energy used. The surplus is purchased at guaranteed prices by the energy distribution company. 
W. Górecki: The new legal regulations concerning renewable sources of energy are beneficial to prosumers. I believe that thanks to the regulations, micro power engineering will develop.  


How long will it take to get back the money that you need to invest in order to become a prosumer? 
W. Luboń: In case of photovoltaic systems, the cost of a system may pay off after about 10 years. But we have to remember that, as in the case of any investment, suitable calculations need to be done beforehand, and they need to answer the question whether installing the system in our local conditions really makes sense.   


According to the act concerning renewable sources of energy, each producer who is at the same time a consumer is supposed to receive a guaranteed amount of money for every kilowatt-hour. As of now, these guaranteed prices are only for the next 15 years. Moreover, such audits do not take into account the fact that the efficiency of panels decreases every year.  
W. Luboń: In our opinion, renewable energy sources are a very good direction, and of course – if only circumstances allow – solar collectors and photovoltaic panels should be installed. Clean energy should definitely be promoted. At the end of the day, the efficiency decrease of these devices is not so large. In case of photovoltaic modules, it is estimated that their efficiency decreases by about 20 per cent after 20 years. Also, even if the guaranteed rates are no longer in place, we will still have a system which will produce energy for us “free of charge”. 
W. Górecki:  I myself have decided to place solar collectors on my house and I am very pleased I have done it. Looking at my electricity bills, I can see I am paying less. Let’s not forget that renewable energy sources do not only mean solar energy collectors and photovoltaic panels, but also heat pumps, which give excellent results. I can speak from my own experience, as a heat pump has proved to be an excellent solution in my house. Unfortunately, I have installed both solutions in an existing house, and as I said before, the best financial results are achieved when we plan the systems of renewable energy sources still at the design stage. That is why it is so important to teach young people what for, how and why a house should be equipped with renewable sources of energy.  


What is your opinion about the government’s photovoltaic programmes? As part of documenting the subject of renewable energy sources, I have ordered today a photovoltaic audit for my house from a company dealing with the installation of photovoltaic systems and helping to obtain a subsidy. To tell the truth, the calculations did not convince me about cost-effectiveness. Although you can receive a subsidy of up to 40 per cent, but for the rest of the amount you need to take out a loan. 
W. Luboń: There are various support programmes, a typical one indeed involving a subsidy with a necessity of taking out a loan. The programme subsidises putting the system in place. Another type of a support system are guaranteed rates, determined by the act of renewable energy sources. In the latter case, we cover the cost of installation, but an advantage is that, firstly, we produce energy for ourselves, and secondly, we resell it to an energy distribution company at guaranteed prices – for example, 0.75 PLN for each kWh. The cost of the installation of a complete system depends on the power output of our panels, and for a detached house it is usually within the range of 20-30 thousand PLN for a 3kW system. If I use up the entire energy that I have produced, I still benefit by saving that 0.65 PLN that I would have to pay for each kilowatt-hour that I need to buy from an energy distribution company. That is why the system of guaranteed rates provides a more reliable profit than in the case of receiving a subsidy for the cost of installing the system, as in the former case, I do not have a loan.
W. Górecki: Many people have doubts, but they can be dispelled by means of providing people with true knowledge of the effectiveness of the methods, as well as suitable calculations made for a particular area, which present the balance of costs and profits. If you can convince investors that the system will generate profits, if you can teach architects, builders and roofers how to design and build passive houses that take advantage of renewable sources of energy, these energy sources will quickly become popular. I also think that an important condition is that the National Fund for Environmental Protection and Water Management becomes part of the education process to a larger extent. As a university, we are heavily involved in promoting renewable energy sources, we conduct research into new technologies, teach students, and deliver lectures in schools. I must admit that our specialisation of Renewable Sources of Energy is very popular. It has been part of the programme for 10 years now.   


What are the forecasts for a technological development of the devices of renewable energy sources, for example, when will the efficiency of photovoltaic panels be doubled? Their production is currently quite expensive, and additionally, their efficiency decreases every year. 
W. Luboń: We can say this: in general, photovoltaic modules are improved every year by means of increasing their efficiency and the use of new materials as semiconductors. Let’s remember that they are also used in space industry, where efficiency reaches even 40 per cent. However, the technologies of photovoltaic modules used in space technologies are extremely expensive. In Miękinia, we have built a comparative system which consists of eleven different photovoltaic modules available on the market. We wanted to compare them with a module of a higher efficiency, but the cost of a several dozen kilowatt-hour module is several thousand PLN. Therefore, it is still not available for us. Modules which can be bought for private use are not so expensive – a 250 watt module is about 800 PLN. An additional cost is a wiring system, an installation kit, and an inverter, which changes direct current into alternating current. These systems have lower and lower prices due to the increasing competition between companies which deal with photovoltaics. An example can be heat pumps – several years ago they were really expensive, also because there was no competition.   


Could you briefly explain how heat pumps work? 
W. Luboń: Heat pumps are devices which can replace conventional heat sources. They are used to heat buildings, produce hot water for household use, and they can also be used to cool rooms in the summer time. They are thermodynamic devices which increase heat from a low-temperature level to a high-temperature level. The easiest way is to compare a heat pump to a fridge; it is cool inside and warm at the back. A fridge or an air-conditioner is about cooling, a pump is about heating. Its operation is based on receiving low-temperature heat from a source such as air, water, ground, a well, or a shallow geothermal source. The installation of a pump is very easy, we only need to decide if we want to have a horizontal ground heat exchanger (placed 1.5-2 metres below the surface of the ground) or a vertical ground heat exchanger (boreholes of up to 100 meters deep). The pump receives low-temperature heat (in the order of several degrees Celsius) and increases it with the use electrical power to the level of 50-60 degrees. Of course, the smaller the difference between the lower and the higher source, the better the efficiency of the pump, i.e. we pay less for electrical energy. These devices work well with surface systems of heat distribution inside the building, such as floor hearing and wall heating.   


What is their efficiency? 
W. Górecki: It is estimated that 1 kWh received from the network gives us in total 4 kWh of heat, so it means that we obtain 3 kWh from air, water and ground. We can say that it is a device based on renewable energy sources, although it also needs energy from the network to be operational. Heat pumps are devices that look good and are quiet in operation. They are a great thing which works very fast and lowers the bills.
W. Luboń: There are also heat pumps that are used to heat water, and they are an alternative to solar energy collectors. At the moment, these pumps are becoming more and more popular in Poland, but they are a solution for people who already have a slow-combustion heater and in the summer they do not want heat water by adding fuel to it on a daily basis. The pump’s operation is based on external or internal air, thanks to which it cools the room a little, and hot water is produced independently of the weather – it makes no difference whether it is raining or the sun is shining. It is important that the air temperature is about 20 degrees Celsius. The installation cost of collectors in a detached house for a family of four is about 10 thousand PLN, and the cost of a heat pump for heating water is about 7-8 thousand PLN.   


There is no doubt that energy from renewable sources is, to a certain extent, an alternative to conventional energy, on one condition, however, that more people and families decide to use renewable sources of energy. If someone wants to have their own, house-based power plant, the investor must be sure that it will prove to be cost-effective. A major role in encouraging people to use renewable energy sources should be fulfilled by the state by means of education and subsidisation. It is worthwhile emphasizing once again that you can save a lot of money if you think about renewable energy sources at the stage of designing a house – it is easier and cheaper to install a micro power station during the construction of a house rather than to change an existing system later.   


Thank you for an extremely interesting conversation and showing me around the AGH UST Education and Research Laboratory of Renewable Sources and Conservation of Energy in Miękinia. All devices that the scientists talked about in this interview can be found in Miękinia. The centre is very impressive, it has been refurbished beautifully, the building is energy-efficient and has all possible conveniences which, of course, are based on renewable energy sources. Even the so-called “greywater”, i.e. rainwater, is not wasted – it is collected in special containers and used in the toilets.