A technical evaluation of the thermal solar collector
systems at Bo01 in Malmö

Abstract: Ten thermal solar collector systems for heating buildings and domestic hot
water at Bo01 in the Western Harbour of Malmö were taken into operation
during the Spring of 2001. The solar collectors are designed to cover about
20% of the total heat demand in that area, with the remaining 80% mainly
covered by a heat pump that brings in heat from a local aquifer.

There are two different kinds of solar collectors in Bo01: a plane
conventional type Solsam LGB-2 AR, and a tube formed (vacuum) type Viessman
200 D. Pumps and valves etc in the solar collector systems are controlled
and monitored by remote controlled computers at “Energifabriken” (G). The
information can be displayed from any place if access-code and connection
to the Internet are available. Nine of the solar collector systems are
connected to the district heating system of Malmö. The tenth system heats
the hot well of an aquifer system. Unlikely many other solar collector
systems in Sweden, there is no heat added from any other production unit to
raise the temperature post the solar collectors. Either the solar
collectors deliver heat by their own (at 65ºC), or there is no heat output
at all.

The systems at Bo01 are reliable solutions with convenient software. Each
system consists of only one type of solar collector, and they also have the
same angle and orientation. In this way they are kept “simple” which makes
it easier to control the pumps and valves, and decreases the risk of
oscillation.

Theoretically, about 12% or 84 MWh/year of the heat from the sun’s
radiation is lost due to non-optimal angles in the solar collectors of
Bo01. This is due to the architecture of the buildings with some roofs
being tilted towards the East and the West, or solar collectors that are
not tilted optimally. In reality the heat loss is much greater because of
dirt on the solar collectors and the effect of shadows.

In Fränsta, the middle of Sweden, there are plans to preheat water with
solar collectors and then add heat from electric water heaters to raise the
temperature before it is used in the district heating system. This is an
efficient technique with great future potential in Sweden.

In the village of Unbyn, northern Sweden, there are plans to build a
thermal solar collector system probably never constructed before. A wood
chip fired furnace supplies heat through a central heating culvert to
customers just like in an ordinary district heating system. Solar
collectors placed on the roofs of the customers´ houses supply heat
primarily to that particular house. In each house there is also a hot water
storage tank equipped with an electric water heater. The tank stores heat
both from the remotely placed furnace and the solar collectors on that
house. When there is a surplus of heat somewhere that a tank is unable to
store, hot water is then passed into the central heating culvert to supply
other customers with heat. An important advantage with this system is that
the furnace can be shut down during summer when the demand for heating is
low and solar energy output is high. This prevents the furnace from
operating at low efficiency due to frequent start-ups and shut-downs.