The team behind a new solar heating plant recently unveiled in Arizona expects the performance not only to be "sensationally high," but that this may turn out to be the solar array with the best output worldwide. The plant provides industrial process hot water -- a sector that could be set to grow very rapidly.
The new plant is providing hot water for a leading sports drink manufacturing plant that produces a well-known sports drink. The solar plant in Phoenix is expected to supply over a million kilowatt-hours (kWh) per year of heat energy to the soft drinks factory — each one of the 892.5 square meters (9605 ft²) of panels producing 1200 kWh/year. The manufacturer also installed a 500-kW solar PV plant on its distribution plant at Tolleson, Arizona at the start of this year and now the two solar plants will be making large savings in conventional energy and make a strong statement for integrating renewables in the brand’s production processes.
The new solar thermal plant serves to preheat the water that is processed into the soft drink process — bringing it from mains water temperature up to a maximum of 35°C (95°F). The system designers have had to build in a number of safety features to guarantee that this maximum temperature is not exceeded, since a higher temperature could damage the membrane in the reverse osmosis water purification system that the heated water passes through in the next stage.
The solar system at the plant went live at the end of December 2008, but because remaining work such as insulation measures still had to be done, the performance monitoring could not start immediately. It will be completed mid-2010 and the team from SOLID expects the numbers to confirm their estimates. There are two reasons behind the optimism — first, Arizona has an outstanding solar resource; second, the efficiency of the thermal collector increases as the temperature is lowered.
SOLID is an Austrian company (now with U.S. and Asian subsidiaries) that specializes in large-scale solar installations for a range of applications. Since 1992, SOLID has been planning, building, delivering, assembling and operating solar plants in excess of 100 m² around the world, providing hot water, heating rooms and supplying process heat, including district heating. SOLID also designs and builds solar-chilled water plants, including the largest commercial solar cooling projects currently in operating.
The plant uses 85, 10.5 m² Gluatmugl solar panels, manufactured in Austria by OEKOTECH. While this is a separate company from SOLID, ownership of the two companies is in the same hands and they work together on their two specialties of manufacture and installation. Gluatmugl is the company’s flagship product and has already won several awards
In Europe, SOLID’s preferred panel size in large plants is 14.3 m². The dimensions of that panel have been optimized for transport by truck. International shipping presents different constraints, so the 10.5 m² panel is designed to fit exactly inside a standard shipping container. This means that installations outside Europe can benefit from the considerable advantages of using large panels.
SOLID’s Harald Blazek, responsible for business and project development outside Europe, explains why large panels are preferable. “It’s partly for the solar efficiency, but mostly for the improvement in the hydraulic conditions, providing more stable results when the system is being run. Large panels make the system more tolerant.”
Being able to lift large areas of module “with one movement of the crane” also has benefits in terms of speed and installation cost. When it comes to the actual collector installation, Blazek says that in Europe, when the larger collectors are in use, it’s quite usual to install up to 600 m² in a day.
All the technical control equipment is assembled in Austria in a standard shipping container with prefabrication and pre-testing performed at the manufacturer’s site. When the container arrives on the erection site, it is simply placed on the prepared foundations and connected to the local interfaces. This “plug and play” approach guarantees a high level of reliability and shortens the erection period on site, says SOLID.
Naturally there’s much more to an installation than simply putting in place the solar collectors. In the case of the Arizona plant, a steel structure had to be placed on the roof to avoid putting pressure on certain parts of the roof. There was also the extensive pipework and installation of the substantial buffer storage tank. Overall, the work took about 3 months, which Harald Blazek says is typical on an installation of this size.
Phoenix, Arizona, is not only the place for the realization of this landmark project but also the headquarters location of SOLID USA. All local coordination was in the hands of SOLID’s U.S. team, led by John Ellers, while the technical background was represented by an experienced technician from the Austria office.
The Arizona project was carried out with the support from U.S. federal solar tax credits and equity finance, with support of the local authorities in Arizona and with excellent co-operation with the Salt River Project (SRP), the local energy provider, explains Harald Blazek. Return on investment is expected in less than 5 years.
Large Is Beautiful
This is one of the first process hot water installations that SOLID has delivered in the United States, and is typical in size — many process hot water installations the company has worked on are about 900 m² in scale. But it depends on the need: in Boston, at Harvard University, the company is working on two schemes to supply hot water to university residences that are 95 m² and 50 m². In Europe, several of the schemes that SOLID is working on, or has in the pipeline, are far larger. For instance, very close to home in Austria a new solar plant supplying energy to Graz District Heating and will provide space heating for the buildings occupied by the water agency of Graz AG. This plant includes 3800 m² (40,000 ft²) of collector area.
“The sector is growing exponentially” says Blazek, “and project sizes are going up all the time.”
Process Heat – A Sector with Great Potential
SOLID CEO, Christian Holter, believes there is huge potential in industrial process hot water, and that this form of onsite energy could rapidly overtake household-scale installations in terms of overall installations worldwide and in terms of the CO2 savings it offers. (To see an interview with Christian Holter, watch the video here.)
Little attention is paid to the heat that goes into industrial processes. Uses include heating of process fluids, washing detergents, heating processes, drying processes and cooling of technical processes. One of the industries with a huge and ongoing demand for industrial process heat (and chilling) is the food and beverage industry. Solar thermal hardly features in this field today, yet a study on solar process heating from an IEA task force calculated that between 3% and 4% of the world’s total industrial heat demand could be met by solar process heat. Even that small percentage of process heat offers higher potential than the whole domestic hot water market.
SOLID will be exhibiting at Intersolar in Munich, May 27th -29th. (Hall B1/stand 443)
Jackie Jones is Chief Editor of Renewable Energy World magazine.
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