Solar power may provide a clean, abundant source of energy, but we know the sun's rays are capable of much, much more. Aside from generating electricity, we've seen solar energy harnessed to produce drinkable water as well, so why not combine the two processes into one system? That's what IBM and its collaborators are hoping to do with an affordable High Concentration Photovoltaic Thermal (HCPVT) system that uses cooling technology from supercomputers to harvest solar energy more efficiently, and produce purified water at the same time.
The current prototype consists of a large parabolic dish made up of several mirrors, connected to a sun-tracking system. The majority of the sunlight hitting the dish is reflected and focused onto hundreds of triple-junction photovoltaic chips, all fitted to microchannel-liquid cooled receivers. Individually, each chip measures just 1 cm x 1 cm and can generates an average of 200–250 watts over an eight-hour period on a sunny day, at an efficiency of about 30 percent.
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Thus far, this roughly matches the electrical power output and basic design of other concentrated solar systems in existence, but the cooling system is what really makes the HCPVT system stand apart. IBM adapted the cooling technology it developed for supercomputers like Aquasar and SuperMUC for use with photovoltaics to create a system that continually pumps water just a few micrometers away from each chip through micro-structured layers.
IBM says this method is 10 times more effective than using air-cooling, and maintains a stable temperature over the chips to prevent them from melting. The cooling system would allow the chips to remain operational at 2,000 times the intensity of the sun's rays, but IBM claims it can still provide a safe temperature up to 5,000 times concentration.
In those IBM's supercomputers, the heat absorbed by the liquid coolant has been used to heat the physical buildings sheltering the system itself, but the HCPVT system developers have a different idea. Instead, the heated waste water could be diverted to a desalination system, where it vaporizes and purifies salt water. The researchers estimate this could produce 30-40 liters of clean water per square meter of the receiver area in a day. Alternatively, the scientists would like to direct the heated water to an adsorption chiller, which could produce air conditioning for a nearby area.
By combining electrical and thermal collection units into a single setup, the research team predicts the HCPVT system would be able to convert 80 percent of the captured solar energy into a usable form.
Another advantage to the HCPVT system is that it would cost considerably less than comparable solar energy systems, while still running more efficiently. Much of the system would be comprised of lightweight concrete and metal foils, as opposed to most other solar collectors that are constructed out of pricier glass and steel, leaving only the small, high-tech components to be produced in Switzerland. This also has the added benefits of lowering the costs for assembly and maintenance, which could potentially expand the number of regions that could implement it.
The research team claims this design would cost less than US$250 for each square meter of aperture area and produce energy at a price of under US$0.10 per kilowatt-hour (kWh). According to IBM, this puts the system on par or lower with energy costs for coal power stations.
Currently, the prototype HCPVT system is being tested at an IBM research lab in Zurich, with additional prototypes planned for Biasca and Rüschlikon, Switzerland in the future. The researchers also hope to begin constructing larger versions of the system in remote locations at some point, but we'll have to see if they can also build the necessary infrastructure needed for such an undertaking.
Scientists at IBM Research, Airlight Energy, ETH Zurich, and Interstate University of Applied Sciences Buchs NTB began collaborating on the project after receiving a three-year grant for US$2.4 million from the Swiss Commission for Technology and Innovation.
IBM Research's manager of advanced thermal packaging, Bruno Michel, explains the HPVCT system further in the video below.