The Warsaw Voice » The Polish Science Voice » Monthly - December 13, 2015
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Warm in Winter, Cool in Summer
A Polish engineer has invented a dual-purpose thermal collector that makes it possible to recover heat from wastewater and store cool air from air-conditioning systems. The device is intended for use in hotels, industrial plants and housing estates.

Hotels and similar buildings discharge masses of hot water into the sewage system. Polish engineer Wiesław Matusiak from the UniHeat company, based in the southern city of Sosnowiec, has built an installation to recover the heat. The device can support both central heating and air-conditioning systems.

UniHeat is a start-up company that specializes in renewable energy technology. Research that led to the certification of the innovative thermal collector was conducted by scientists from the Wrocław University of Environmental and Life Sciences and the Institute of Renewable Energy at the AGH University of Science and Technology in Cracow.

“Wastewater offers enormous potential in terms of energy,” says Paweł Matusiak, son of the inventor and CEO of UniHeat. “The idea is to recover energy from wastewater using heat pumps. When used in a hotel, our system pays back in five to seven years.”

Internationally, technology for recovering heat from wastewater is especially popular in Germany and Switzerland. The first such installations hit the market seven years ago, according to Paweł
Matusiak. Experts estimate that 800 terawatts of energy is contained in household wastewater worldwide a year, and a further 700 terawatts is wasted in industrial wastewater every year. According to consulting firm Deloitte, in Poland alone the market for the recovery of energy from wastewater is worth 80 million euros annually.

The membrane thermal collector designed by Wiesław Matusiak is also capable of storing cool air. This is invaluable in summer when hotels and offices are air-conditioned. The market for such devices is estimated to be worth 24 million euros a year.

“The main point is to learn how to separate ice from the surface of the heat exchanger, the device that recovers energy,” says the younger Matusiak. “If we have water with a temperature of 10 degrees Celsius and want to recover energy from it, it needs to be turned into ice, which will then cover the exchanger. If the exchanger becomes covered with ice, it stops working. The idea behind the invention is to separate the ice and thus enable the device to operate continuously and regenerate without being switched off. The chiller function supports the work of the air-conditioning system. If the air conditioner can be switched on at night, it will be more efficient and the ice accumulated will ensure air conditioning during the day.”

In some countries such as Spain, there are sometimes power outages in summer because the network is overloaded by air-conditioning systems. This past summer the same happened in Poland for the first time. Devices such as chillers are designed to prevent the network from becoming overloaded. They have already passed the prototype stage, and large industrial units have been manufactured.

To obtain co-financing for their technology, the inventors worked for two years with researchers from the University of Life Sciences in Wrocław, who conducted a technical analysis and a feasibility study for the invention. The UniHeat company also established training and research ties with the Institute of Renewable Energy at the AGH University of Science and Technology in Cracow.

In the United States, chiller systems have been used for more than two decades. The Polish system is a lot less expensive to use, according to Matusiak: its operating cost is 20 euros per kilowatt, while its U.S. counterparts’ operating cost is about 70 euros per kilowatt.

The invention will be used in projects co-financed by Poland’s National Center for Research and Development (NCBR) under its Demonstrator Plus program. A pilot system based on the innovative technology developed by UniHeat will be installed in a residential estate.

The invention is also intended for use in passive houses—environmentally friendly, energy-efficient buildings that meet stringent requirements regarding ventilation and energy consumption. A major problem is that such buildings tend to overheat in summer. Whatever is saved on heating in winter has to be spent on air conditioning in summer. Heating the building in winter produces ice as waste.

“We have designed a system that collects the ice and so we have air conditioning in the summer for free,” says Paweł Matusiak. “We have found a solution to an important problem, especially as passive construction is set to take off around 2020 as a condition of obtaining a building permit.”

The thermal collector has attracted a variety of prospective customers including air-conditioning system producers. UniHeat has submitted the invention for intellectual property protection under the Patent Cooperation Treaty (PCT) procedure.
Karolina Olszewska