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By the simple keywords “cshp” and “+solar” you find the most important links to online resources on large-scale solar heating. Her you get the Google query.

Evaluation of Test Method for Large Solar Collector Efficiency

The Technical University of Denmark does research in large-scale solar collectors.

Abstract from DTU-homepage regarding the conference publication:

The test method of the standard EN12975-2 (European Committee for Standardization, 2004) is used by European test laboratories to determine the efficiency of solar collectors. In the test methods the mean solar collector fluid temperature in the solar collector, Tm is determined by the approximated equation where Tin is the inlet temperature to the collector and Tout is the outlet temperature from the collector. The specific heat of the solar collector fluid is in the test method as an approximation determined as a constant equal to the specific heat of the solar collector fluid at the temperature Tm. The power produced by the solar collector during a test period is determined by the product of the specific heat, the mass flow rate and the temperature increase of the solar collector fluid. The solar collector efficiency is in the standard determined by measurements at different temperature levels. Based on these efficiencies, an efficiency equation is determined by regression analysis. In the test method, there are no requirements on the ambient air temperature and the sky temperature. The paper will present an evaluation of the test method for a 12.5 m² flat plate solar collector panel from Arcon Solvarme A/S. The solar collector panel investigated has 16 parallel connected horizontal absorber fins. CFD (Computational Fluid Dynamics) simulations, calculations with a solar collector simulation program SOLEFF (Rasmussen and Svendsen, 1996) and thermal experiments are carried out in the investigation. The investigations elucidate: • How the mean solar collector fluid temperature Tm is underestimated by the approximated equation in the test standard and how the collector efficiency equation is influenced by the underestimation of Tm. The dependence of the volume flow rate is shown; • How the use of the approximated specific heat of the solar collector fluid is influencing the collector efficiency expression; • How the temperature levels used is influencing the collector efficiency expression; • How the measured collector efficiency is influenced by the weather conditions such as the ambient air temperature and the sky temperature. Based on the investigations, recommendations for change of the test methods and test conditions are considered. The investigations are carried out within the NEGST (New Generation of Solar Thermal Systems) project financed by EU.

Big players are waking up in Denmark

For the first time, a major district heating company is planing to adopt the concept of central solar heating. The company VEKS, distributing heat in the western part of the Copenhagen area is aiming at a CSHP with a solar collector size of 20,000 m2, placed along a main highway. The plant will match the current record of the Marstal plant, also placed in Denmark. The plant will deliver approx. the heat of 5-6,000 single family houses.CEO, Lars Gulev, of the “Vestegnens Kraftvarmeselskab” district heating company estimates the plant to produce 10 GWh heat to the district heating system. The goal is to get the plant into production before the International Climate Conference in Copenhagen, 2009, where the expectations are to replace the Kyoto-protocol with a more ambitious protocol.

It is expected that the application of central solar heating is a factor 4 more cost efficient compare to single family housing solar installations.

Relevant is to mention, that the company is expecting lower production prices for the solar plant compared to the traditional co-generation plants due to the facts that solar prices are reduced as conventional heating prices are increased during the later years.

“In the first place, the solar heating plant is planed due to commercial reasons. Getting reduced CO2 pollution is a environmental side effect.” says Lars Gulev.

We hope others will take this considerations up and CSHP will play a more dominant role in the future of district heating. It would be interesting to see, if surplus heat from the power production will be cooled into the see due to this investment.

You find information on VEKS’s homepage on http://www.veks.dk (in Danish), where you change to English and will be presented for general information on the district heating system of Copenhagen. The solar plant is presented at the location http://www.veks.dk/Artikler/Seneste%20nyt/Solvarme.aspx

Brænderstrup CSHP

The Danish Engineering Newspaper did present the following news about a new very large CSHP plant:

Place: Denmark, Brænderup (near Horsens), at the mainland.

Size: 8.000 m² solar collector field, sized to deliver 10% of the district heating demand.

Of the 13 million total cost, the 3.5 millioner DDK are funded by a public body, Energinet.dk, that last year did analyse solar and district heating lead to positiv economical results. This analysis pointed out that this is due to the fact that the heat- or power plant can be turned of for some periods, where the price for power is too low to produce.
The maximum effect is estimated to 6 MW heat, with an annual production of approx. 4,000 MWh heat, leading to a yearly emission reduction of 4,300 tons CO2. The plant is designed by consultant company Planenergi and Ramboll, Denmark with Arcon solar collector producer, the same companies as involved in most of the plants in Denmark.