# marketing our solar home

Discussion in 'Home Power and Microgeneration' started by Adam Webster, Nov 16, 2003.

2. ### Cor StijgersGuest

I like your pictures very much!

I understand that you may have some experience with heating the house on
solar energy?

I'm considering to heat my future home on solar power, but I can not
find much information on the Internet on heating. Most of the
information is about heating tapwater. We do not use much hot tapwater,
so we don't expect serious savings there.

I wonder how many square meters solar collectors are needed and
how many liters storage for the hot water. Do you have any experience on
this, or do you know where I can get some information?

kind regards
Cor Stijgers, Amsterdam

3. ### EcnerwalGuest

This question is a great deal like asking "How long is a piece of
string?"

With no information about where the house is, what size it is, what the
incoming sun resouce is, the local climate, the specific values of
insulation, it's quite impossible to say how many square meters of solar
collector you need, or how much hot water storage you need.

In a mild climate - less. In a harsh climate - more. Few cloudy days in
a row - less. Many cloudy days in a row - more. Well insulated - less.
Poorly insulated - more.
alt.solar.thermal - read the archives for a lot of solar house heating
and house site. I'm guessing, since you asked about square meters of
collector, that we'll need to try to recall what the European R-values
for insulation actually refer to, since most regulars on that group are
using US R-values based on imperial units and will need to convert to
consider your design, and I'm not recalling what the underlying units
for the metric version of the same number are.

4. ### Nick PineGuest

Simple sunspaces are cheaper than "solar collectors."
We can make things up... If 3 kWh/m^2 of sun falls on a south wall on an
average 0 C day and the 20 C house has 50 W/C (284 Btu/h-F) of conductance,
it needs 24h(20-0)50 = 24K kWh/day (82K Btu/day) of heat. If a square meter
of U2.8 (US U0.5) sunspace glazing with 80% solar transmission collects
2.4 kWh over 6 hours on an average day and loses 6h(20-0)1m^2xU2.8 = 336 Wh,
for a net gain of about 2 kWh, the sunspace needs about 24K/2 = 12 m^2 (129
ft^2) of glazing. If we needs 5x24 = 120 kWh for 5 cloudy days in a row and
a liter of water releases 1.16Wh/kgC(70-20) = 58 Wh as it cools from 70 to
20 C, the house needs 120K/58 = 2069 liters of cloudy day storage.
R-values are measured in W/mC, conductance is measured in mC/W, and
US R5.68 (Btu/h-F) becomes European U1 (W/C.)

Nick

5. ### NewsGuest

If you want to heat your house using solar energy, using a wet system, it is
best to use a low temperature operation underfloor heating system. Using
low temperature operation mean that even in winter you may be able to use
low temperature hot water effectively. Have the roof panels, or better the
whole of the south side of the roof, heat a large thermal store cylinder.
The lower section of the thermals store should be used to heat the
underfloor pipes, with the top section to heat the domestic hot water - if
there is not enough high temperature heat for domestic hot water
supplementary heating can heat just the top section. The thermal store
should be sized to give 3-4 days of heat in cloudy conditions if possible,
depending on climate of course.

6. ### NewsGuest

Heat exchangers for forced air systems require high temperatures, otherwise
draughts occur. That is why low temp underfloor heating is ideal for this
application. How did it manage with the forced air?
Was yours \$25 per month?