Heat balances of the solar heating systems in 2002. http://www.kolumbus.fi/solpros/reports/ISES_ekoviikki.pdf

Figure 6: Heat balances of the solar heating systems in
2002.
The amount of auxiliary heat (district heat) varies from
29 to 45 kWh/m3,yr and well meets the Ekoviikki design
criteria. The values shown include all heat used (space
heating, dhw, losses). In case of the Skanska 1, the
specific space heating load is 50 kWh/m2, yr. The solar
heat represents in average some 10% of all heat demand,
but for Skanska 1it is as high as 22%.
A yearly solar performance analysis is shown in Figure
7. The net solar output is around 300 kWh/m2,yr (incl. all
heat losses). Skanska 1 system yields almost 400
kWh/m2,yr which is very high output in Finnish
conditions. Taking the long piping lengths in the multistoried
house from roof to the storage, and in some
houses also the connecting pipes in the ground, the gross
output of the collectors can be viewed very good. In one
system (Helas), the heat withdrawal subsystem was not
yet fully operational and hence the collector output not
comparable to other systems.
The share of the solar heat of the domestic hot water is
around 30% but in some sites we found even 60-70%
which for a small part is also explained by solar dhw use
for bath floor heating.
In two sites, both space and dhw heat are measured.
These measurements showed that the dhw profile was not
as even as previously assumed. Figure 8 shows the
monthly values for the Helas site (26 dwellings). The
dhw clearly drops in midsummer during the summer
vacation period. The monthly peak is found in January-
February and it is almost twice that of the summer valley.