An item for the discussion of solar power in the home, including solar
panels that heat water, panels that generate electricity and also use
of "passive solar" design.

28 responses total.

In a few years my house will probably need a new roof.  If we don't
outgrow the house and like it, the neigbourhood, city and school
district enough to stay there for at least five *more* years, I would
like to have photovoltaic (PV) solar panels installed on the new roof
to generate electricity for use in the house.

I expect we will need the panels, a charge controller, a bank of
batteries, at least one inverter and perhaps some sort of grid tie-in
so that we can sell any surplus electricity to the power company.  Any
constructive comments or advice would be welcome.

Look for some solar-power organization where you live to ask if you can sell
power to the 'grid' and what they pay, and whether it will come even close
to breaking even.  Solar hot water is probably cheaper to install.  We could
put you in touch with someone here who sells and installs the panels (a
friend) and has some unusually cheap models made and used in China.

"breaking even" in terms of the cost of the grid-tie, or the complete
system?  I have seen a house not far from here that appears to have
solar hot water panels.  I've no idea how well that works for them, or
how complex it would be to install.

Why not ask the owners?  Jim's neighbors took out their system and gave him
the solar panel.  The only solar to electric setup I know of here will
probably never pay for itself.  They are doing it to prove it can be done.
Eventually panel costs will come down.  Batteries only last 10-20 years and
are expensive.  Usually the power companies only pay you some minimum rate,
much less than they are charging at the same time (during summer peaks it can
be 5 to 1).  Unless you are running a central air conditioner, you will have
summer excess power if you try to put in enough panels to get anything in
winter (especially in Michigan where winters are cloudy).

I have heard that thin-film developments will help to bring the cost
of photovoltaics down.  If selling electricity is not practical then I
suppose we might have the option of going off-the-grid, eliminating
the need for the grid tie but perhaps requiring more battery capacity
to take us through the night.  Hopefully it will be a few years before
the roof really needs replacing, so the costs and benefits seem likely
to change before I have to make a decision.

You need to plan for several cloudy days in a row, and for not having much
sun in December.

I wonder whether ordinary water heaters object to having warm water fed
to them.  If the tank were fed via solar panels, it might require less
energy during the sunnier parts of the year.  I suppose during the
winter it's that much more pipe to heat though.

Insulate the pipes.  I think it is standard practice to solar preheat water
going to the main tank.

I plan to insulate many of the pipes here.  I'm told that heat tape is
standard issue too because of the cold, but I have yet to use that.

Heat tape will waste more heat (electrical) than would have been lost from 
the pipes: instead, insulate.

Or insulate OVER the heat tapes.

Re #11: I'm told that's the usual procedure here.  So far I've not done
it and there was only one brief time when the pipes froze, with a wind
from the West.  That reminds me I should get insulating before the cold
sets in.

What's the situation that your pipes can freeze? Most homes in Michigan are
built so that pipes will not freeze (actually, the water in them) if the home
is kept at a normal living temperature. 

If your pipes are in the crawl space, insulate the crawlspace walls.  You can
put foam boards on the outside and cover them with stucco (or maybe cement
board).  Is there any pipe insulation?

Around here, many dirt-floored crawlspaces were dug deeper to become
basements.

Re #13: I can think of several places where the (water in the) pipe may
have frozen, including a run along the inside the garage's west wall.  I
need to insulate that pipe as soon as  I can get to it and perhaps keep
an eye on the temperature on that wall.

Re #14: Some pipes are in the crawlspace, including one that
reverberates horribly after a toilet is flushed.  The crawlspace has no
freeboard because the house is flush with the ground.  The crawlspace is
really more of a pit dug under the house.  I should install some
thermometers in the crawlspace.

Does it snow there?  Here crawl spaces have to extend at least a foot above
ground.  Areas with more snow probably require more than that.  Why is your
plumbing going through the garage, and can it be rerouted through the
crawlspace instead?  What is a freeboard?

I will ask Jim what might be making the noise.  Water hammer occurs when
valves are shut suddenly but toilets usually fill slowly.

Some toilet valves shut off quite suddently, and could cause water hammer.
There should be a damper in the pipe network somewhere.

Water can feeze in pipes without bursting them. Pipes only burst when water
freezes after being trapped between fittings in which water freezes first.

Re #16: it snows here enough to spend hours shovelling snow.  Freeboard
is the side of a boat between the waterline and the gunwhale.  In this
context I used it to mean the part of a house between the ground and the
floor.  Come to think of it, we have a front door step, but when you
subtract the thickness of the floor, there's probably little if any
freeboard left and that's all brick anyway.  I'm glad the pipe runs
along the inside of the wall rather than through the crawlspace.  At
least I can get to it to work on it.

    If I could scrape together enough money to fix up this
house (but not enough money to just bulldoze it and build
something new), I would ideally have a solar hot water panel
for faucets, shower etc, another for underfloor radiant heat
and at least one photovoltaic array for pumping water out of
the ground.  Not sure how much of this is practical given
Illinois' climate.

It is possible to heat a house even in a northern climate with solar
heat (although they do apparently use some propane). I dont know how
well such a system would work in Michigan or Illinois where it is cloudy
for much of the winter. 

http://www.solarhouse.com/

With enough insulation the normal activities in the house might generate
enough warmth.

And moisture....

New technology seems to have worked out the moisture problem

http://www.nytimes.com/2008/12/27/world/europe/27house.html

We dehumidify all winter.  Cooking with a pressure cooker does not generate
much moisture (or heat).  

Dehumidifiers also add net heat to the house (an observation, not an 
argument). However they do not remove accumulatikng CO2 or CO or other 
toxic gases.

The technology slynne cites in #23 is very good - for retainng heat and 
eliminating accumulating moisture. However it does not work in reverse - 
for cooling - as suggested. People and all activities generate net heat. 
Nothing generates net "cool". The suggested heat exchanger could allow 
air circulation with the inside cooler than the outside, but a 
refrigeration system would be required to make up for the inefficiencies 
of the heat exchanger.

Would it be possible to allow circulation in the summer with the heat
exchanger portion turned off? That would work in places where it gets
cool at night. 

You might as well just open windows at night. But yes, you could bypass the
exchanger at night and use its fan to circulate air.

Perhaps there's a reason forced air and refrigeration are the default
option here then.  :-/

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