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Photovoltaic-thermal (PVT) collectors can provide heat and electricity. A quasi-stationary model of a PVT collector is presented and validated based on measured data. Subsequently, the electrical and thermal performance of such a collector is simulated for different locations. These simulations focus on different flow rate control approaches with the aim of maximizing the electrical yield. The simulation results show that the two control approaches presented in this paper have the potential to increase the electrical output for all locations. The increase in additional electrical output at locations with higher solar radiation is significantly higher than the increase in solar radiation between the locations investigated. Additionally, the cooling fluids’ temperature differences for such PVT collectors vary between the investigated control approaches, where variable flow rates lead to a steadier increase in cooling fluids’ temperature. In conclusion, the flow rate needs to be adopted to the pre-defined main goal of the respective PVT collector. The use of variable flow rates by providing low-temperature heat at a more constant temperature level appears to be advantageous in this context.

Special report: Although new wind and solar projects tend to dominate the headlines, it's actually hydropower that reigns supreme in terms of both the amount of renewable energy electricity generated and new installed capacity. Overall, newly installed renewable electricity capacity grew 6%, despite a double-digit dip in overall renewable energy investment.

The World-Market Status special report – Although still relatively small, the geothermal market has shown strong growth in 2015, and some favorable condition may soon give it a boost. The pacific “ring of fire” countries are the sole manufacturers of geothermal power, with the US leading as the biggest single producer of electricity from geothermal energy.

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DESPITE THE INTERNATIONAL ECONOMIC CRISIS AND THE REDUCTION OF GOVERNMENT INCENTIVES, RENEWABLE ENERGY IS CONTINUING TO HAVE A GROWING IMPACT ON THE WORLD ENERGY MARKET. EXPERTS FROM LAHMEYER INTERNATIONAL AND THE DEUTSCHES BIOMASSEFORSCHUNGSZENTRUM EXAMINE THE 2009 STATISTICS, AND HIGHLIGHT NEWLY-INSTALLED CAPACITY, MAJOR TECHNOLOGICAL DEVELOPMENTS AND EMERGING MARKET TRENDS.