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New: Research Information from BINE in the Solar Magazine
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The System of the Month for January 2001 is a prelude to the cooperation
between the Solarserver and BINE, the information service for new
energy techniques and their uses. The goal of the cooperation is
to introduce research results to the general public.
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Product of the Month/ January 2001
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Local Solar Heating Systems for the Eco-City
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Concepts in city planning are being increasingly developed,
in which the provision of renewable energy in housing developments
is playing a main role. However, in comparison to the design
of individual one-family houses, solar collectors for entire villages
are still rarely planned.
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Research and trials of systems that combine collector surfaces
of over 100 square meters with large-dimensioned long-term storage
have been in use for about a decade: the Federal German Government
gave the starting shot for 7 pilot programs with the Sponsorship
program " Solar Heat 2000". BINE Info 8/99 drew the balance
and allowed a glance into the future.
Photo: pilot system in Steinfurt-Borghorst
Source: BINE Information Service
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Solar Coverage Rate-40-60%
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Coordinated total concepts that largely encompass heat protection
and efficient energy production, were standing by at the beginning
of the pilot project. Systems with long-term heat storage were
brought into operation in 1996 in Hamburg and Friedrichshafen, and
in 1999 in Neckarsulm. All three systems were constructed, for economical
purposes, to contribute almost two thirds of the entire heat consumption
for household heating and hot water through solar rays. A comparison
of solar heating costs shows, that local heating systems work more
efficiently than the solar heating systems in one- and multi-family
houses: a kilowatt hour produced with a typical small solar heating
system (one to two square meters of collector surface per person)
costs 30 to 60 pfennigs. Local heating systems with short-term storage
supply, according to the calculations of the researchers, the same
heat for 15 to 30 pfennigs. A kilowatt hour of solar heat from a
system with long-term storage could cost between 33 and 55 pfennigs.
In any case, the less expensive system-costs of the larger systems
make local heating systems more attractive.
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Scheme for solar supported local heating
system with seasonal heat storage
and direct or indirect heating system connection.
Graphic: BINE Information Service
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Four types of storage are in operation, that are being used
in reference to the particular geological conditions. Hot water
storage tanks were preferred in Hamburg, Hannover and Friedrichshafen;
in Neckarsulm subterranean tube storage; and solar heat is stored
in gravel and water in Steinfurt and Chemnitz. The system with the
most modern solar roof is in Rostock. Windows and blind elements
are integrated in the solar roof of the "Helios" building.
All collector backs are ventilated: the humidity that comes out
of the building and under the collector can be siphoned off. Since
the end of 1999, a ground water heat storage tank (Aquifer tank)
has been in operation in Rostock. The system supplies 108 apartments
with hot water and supports the heating . The production from the
collector with a surface of 1,000 square meters is fed into the
20,000 cubic meter storage tank. A low temperature heating system
with radiators lowers the return temperature and creates more economical
operating conditions for the solar heating system. The Technical
University of Chemnitz calculated a solar heating price of 47 pfennigs
per kilowatt hour.
Experience and Outlook
The heating system layout and the type of domestic water heating
determine the return temperature of the local solar heating network
and thus the solar heat yield . A higher available solar heat
capacity is reachable with low temperature heating systems than
compared to a conventional heating system. Indeed, these systems
generate additional costs, and it depends on the commitment of the
builder and the planner, if they will be realized. The "Helios"
Project is valued as proof, that low-temperature heating systems
are possible even in apartment buildings. The percentage of solar
coverage of the local heating supply can be increased through direct
connection to the heating system: not using a heat exchanger sinks
the return temperature to approximately 40 degrees Celsius. This
means a solar gain of 7%.
Frequent flaws were ascertained in conventional house technology
during the pilot tests. Hydraulically irregular water and room
heating systems, plate-heat exchangers with too little transfer
power and regulation problems in outdoor temperature controlled
heating systems are restricting efficient energy use. The operator
of the local solar heating system can have little influence here--the
local solar heating system stops at the house switch. In order for
the solar heat production to be efficiently used, all participants,
especially the implementing companies, have to be included and motivated.
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The testing and development phase is not yet concluded. In the
past years, the basic concepts were endorsed, weak points were analysed
and ways to increase efficiency were presented. High investment
costs remain an obstacle for operators and the housing market. New
financing concepts could help with this.
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1000 square meter solar roof: multi-family house
"Helios" in Rostock |
Without state sponsorship, only local solar heating systems with
short term storage could, in the foreseeable future, come into efficient
operation . The goal of the long-term storage system is to reach
prices that, without sponsorship, would be at the most twice as
high as those for heat from natural gas or oil.
Photo: BINE Information Service
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Materials and Illustrations: BINE Information Service FIZ Karlsruhe
Solar Server Editorial Staff: Rolf
Hug
Translation: Mary Meier
Further information: www.bine.info
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Further Solar Energy Systems of the Month:
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