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Solar hot water install uneconomic if heat pump installed ... opinions please ...

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Posted by Adrian on October 14, 2006, 7:56 am
Hi All

Just moved to e new house out here in the far South-West of Ireland -
lovely ! <g>

Considering options for heating / hot water & etc.

Currently have oil-fired boiler for central heating, also heats the
domestic hot water, with electric immersion for backup water heating.

Before moving out here, I was thinking of installing an evacuated
collector system on the roof for domestic hot water, with (possibly) a
ground-source heat-pump for space heating. We have plenty of room for
the 'slinky' pipe collector - and have to do some 'earth-moving'
anyway in order to sort out some levels - so installation costs on the
pipework would be part of another project.

Next-door house already has a heat-pump system. Their installer
advised them that, if they were going for a heat-pump system, then it
was not going to be cost-effective to also install solar thermal for
the hot water.....

Would welcome opinions on this statement...

Many thanks

Posted by Blue Cat on October 14, 2006, 1:14 pm

Whether a solar hot water system is feasible with an existing heat pump
system depends on how much sunshine is available in your area. If you have
extended periods of cloudy weather, a solar hot water system may not be
worth the cost.

Posted by Adrian on October 14, 2006, 7:49 pm


Thanks for the comments...

We seem to be subject to a sort of microclimate (near to the
south-west coast) - and weather can vary considerably from hour to
hour.... weather forecasts are interesting only a a source of
amusement <g>

I can fit solar fairly cheaply myself - and I guess that it could be
useful during the summer months.....


Posted by bob.rohatensky on October 14, 2006, 2:25 pm
 You might find this interesting:

It is a demonstration project to use thermal capture/storage for home
heating in a planned community. They have solar thermal collectors
across all of the garage roofs and use a grid of 30M boreholes with
pipe loops for seasonal thermal storage.

Each home _also_ has individual solar domestic hot water panels.

I have been working on a similar concept to the Drake Landing idea, but
by using indirect solar capture from ambient air thermal energy and a
solar powered absorption heat pump I believe that the required amount
of solar collectors can be reduced by 80% with a small amount of
electrical power output as a by-product.

In an implementation for a single dwelling, if the tower is low (i.e.
30 meters), and the intent is for thermal capture, there wouldn't be
any substantial electrical power generation, but it should be possible
to have the system power it's own pumps.

Adrian wrote:

Posted by Adrian on October 14, 2006, 7:53 pm
 HI Bob

On 14 Oct 2006 07:25:43 -0700, bob.rohatensky@sasktel.net wrote:

Thanks for the link - but I'm stuck on a slow dial-up connection at
the moment and the site's taking 'forever' to load.... - I'll look
again in a couple of weeks time when my wireless broadband should be

Bit more complicated than I was planning <g>

Interesting - all the same - thanks !


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