Blog Post

A Cutting-Edge Hybrid Solar-Thermal-PV Collector from Turkey

There's an exciting new hybrid solar collector from Turkey that combines photovoltaic (PV) power generation with solar water heating. The idea of combining PV and solar-thermal isn't new, but Solimpeks Solar Energy Corp. has taken the idea to a new level of sophistication with their Volther hybrid solar collector.

The beauty of combining PV and solar-thermal is that by cooling off the PV modules, the efficiency goes up. According to the company, PV modules lose approximately 0.5% of output for every degree-Celsius of temperature rise. Jahannes Hoek, the R&D Manager at Solimpeks, claims that the PV efficiency has been tested as high as 28%, while producing 60-70°C (140 – 160°F) water. Kemal I'bis, the director of communications at Solimpeks, told me that "A Volther Hybrid PV-T panel, stabilized at an average of 45°C (113°F) will produce roughly 20% more [electrical] output over a 12-month period, when compared to a PV system with the same peak output." Keeping the collectors cooler also improves module life. The Solimpeks Volther comes in two models. The PowerVolt collector (W-175/500) is optimized for electricity production, producing 175 watts of peak electrical output and 460 watts (1,570 Btu/hour) of thermal output. The PowerTherm collector (M-106/750) is optimized for hot water production by having an extra layer of low-iron solar glass; the peak electrical output is 160 watts and the solar thermal output is 610 watts (2,080 Btu/hour). According to I'bis, this is roughly 80% of the output of one of their standard solar-thermal collectors.

All of the Volther collectors use monocrystalline silicon cells. The solar water heating system uses copper tubing and heat exchanger and circulates an antifreeze solution for freeze protection. The integrated collector is housed in an aluminum box.

While the company's standard solar panels carry a warranty of 10 years and have a projected service life of over 30 years, Solimpeks warranties the Volther panels for 25 years and projects a service life of over 35 years, Hoek said in the interview.

Solimpeks is not new to the solar field. The company was founded more than 30 years ago in 1979, and is a leading supplier of solar collector systems worldwide. More than 25 of the new Volther systems have been installed to date, mostly in Turkey and Western Europe (including Germany, England, and Spain). The company's broader product line is exported to 60 countries, with European Union countries comprising about 70% of sales.

The company currently does not have an exclusive U.S. or North American distributor, but exports product directly from Turkey. North America currently accounts for approximately 5% of total Solinpeks sales, though none of the Volthers hybrid collectors have yet been installed here. The company hopes to grow sales in North America once a full distribution network is established. Solimpeks hopes to eventually challenge the big players and capture 10% of the North American market, according to I'bis.


BuildingGreen relies on our premium members, not on advertisers. Help make our work possible.

See membership options »

In May, 2010, Newform Energy completed the first Volther installation in England (see photo). The system, installed at the Surrey Children's Home on the outskirts of London, consists of 48 Volther hybrid collectors (24 each of the PowerVolt and PowerTherm collectors). The peak output for the system is 7.9 kW(e) and 27.4 kW(t), and the net annual energy production is projected to be 8,000 kWh(e) and 14,000 kWh(t).

Solimpeks collectors and systems carry 18 certifications worldwide, including that of the Solar Ratings and Certifications Corp. (SRCC) in the U.S.

Volther collectors carry a price premium over stand-alone PV or stand-alone solar-thermal collectors. According to I'bis, the collectors are approximately 60% more expensive than Solimpeks solar-thermal collectors and 50% more expensive than their stand-alone PV modules. But the total system cost for the hybrid Volther system is approximately 20% lower than installing separate systems for PV and solar hot water. Additionally, installing just a single style of collector on a roof offers aesthetic appeal over different-looking PV and solar-thermal panels.

If the Solimpeks Volther panels perform as well as claimed and if reliability proves itself, this could be a breakthrough product that simplifies solar installations. The company claims that 25 square meters (270 square feet) of collector would be enough for an average northern European home to meet both hot water and electrical demand, averaged over the course of the year.

For more information:

Solimpeks Solar Energy Corp.

Karatay, Turkey

+90 332 444 06 02

I invite you to share comments on this blog. Do you think there's a market for hybrid PV-thermal collectors in North America?

Alex Wilson is the executive editor of Environmental Building News and founder of BuildingGreen, LLC. To keep up with his latest articles and musings, you can sign up for his Twitter feeds.

Photo: Solimpeks Corp.

See more on this product in the GreenSpec Guide

Published June 10, 2010

(2010, June 10). A Cutting-Edge Hybrid Solar-Thermal-PV Collector from Turkey. Retrieved from

Add new comment

To post a comment, you need to register for a BuildingGreen Basic membership (free) or login to your existing profile.


July 13, 2010 - 8:42 am

The installation cost savings and architectural benefits seem attractive. Studies I've read, however, indicate that performance increases in the PV due to cooling by the solar thermal loop are at a cost of thermal collector efficiency. Total performance of the hybrid system is likely a wash over separate systems—marginally better PV, but poorer thermal. Such a system would therefore, one might surmise, perform better overall in a cooling-load dominated climate or season, where electrical loads would outweigh domestic hot water needs.

January 26, 2011 - 8:44 pm

A solar water heater is a long-term investment that will save you money and energy for many years. Like other renewable energy systems, solar water heaters minimize the environmental effects of enjoying a comfortable, modern lifestyle.a solar system can reduce energy costs and provide a reliable supply of domestic hot water.

July 19, 2010 - 8:09 pm

If I can't buy these in the USA, where do I sign up to be a dealer/distributor? Though the Germans had an exclusive on these hybrids. Where roof space is limited, these are perfect.

June 11, 2010 - 7:04 am

Climate change is a global problem, and yet each one of us has the power to make a difference. Even small changes in our daily behaviour can help prevent greenhouse gas emissions without affecting our quality of life. In fact, they can help save us money!

June 16, 2010 - 10:06 pm

What about prices?

September 22, 2010 - 5:09 am

Here is the thing, unless I read it wrong, these collectors need to work on a closed loop glycol operating system on the thermal side. Keep that thought on the side for a moment. Now, at this point we know the biggest advantage of these collectors is for them to cool off the PV cells. So this product would suit well for tropical warm areas where PV cells lose efficiency due to high temperatures. On the other hand, in these non-freezing tropical areas, people use open loop passive thermal systems like the thermosyphons which are usually half the cost of glycol operating thermal system. My question is, unless we are talking about a huge commercial project, can the price of these collectors really compete with open loop thermal systems, or are we just talking about a slightly higher efficiency PV cells with double the cost? What's essential to know at this point is the quality of these collectors. In case of any leak on the thermal side, we would have devastating results on the whole system. I love the idea, but never forget, "electricity and water doesn't mix"

June 21, 2010 - 1:11 pm

The advantages of having a dual system would outweigh the concerns of overheating the cells and would in fact help cool them in the summer months. I would look for more companies to follow suit with this type of application in the near future.