DC heat? [RE-wrenches]

[Ian Woofenden, Home Power]

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Geoff,

There's nothing inherently wrong with making heat with renewable 
electricity, and wind and heating are a great match in many places. 
Using RE is certainly better than using fossil fuels. It's just been 
a financially difficult decision with dino-fuels cheap and RE gear 
expensive in the toddlerhood of RE. We need to make sure we don't 
take our 20-year-old off-grid mindset into the future. The goal 
should be to have _everything_ powered with renewable energy.

That said, there are better and worse ways to use the technology, and 
we should focus on the most efficient applications possible. Consider 
using a heat pump to get more bang for your buck on your Bolivian 
project. I know a few people playing with these with hydro systems, 
and I'm tempted to get one to use my surplus wind energy when the 
kids leave home and leave us an energy surplus. With a 3:1 COP, you 
cut the size of your wind turbine to a third compared to the same 
amount of resistance heat, unless I'm missing something. Contact me 
off-list for contact info for the hydro/heat pump folks. Though 
theirs are small applications compared to yours, they may be able to 
give you some insight

Best,

Ian


>------------------------------------------------------------
>
>Happy holidays all you listers...
>
>I have been presented with an interesting customer design I want to
>improve...
>
>They have an S-load of wind (15 m/s... about 7kw most of the time) and are
>looking at a Bergey 7.5 48 volt unit with a pair of VFX3648s and a string of
>L-16s.  Very few AC loads - mostly they plan on powering an electric hot
>water tank that will serve a radiant floor system (all yet to be built).
>
>So - doesn't it mak a lot more sense to A) heat the water with DC elements
>eliminating the conversion loss and or B) heat the slab directly with some
>sort of DC resistance wire....
>
>And if B, then C - where and what (I have seen AC floor heating grids - any
>source for DC?)
>
>The entire concept of "heating" with renewable energy (other than passive
>solar) is so foreign to me that my brain locks up just going there.  BTW -
>this is a birth center/health clinic in Bolivia.  Already planning on a
>voltage relay to take out the heat circuit at low voltage.
>
>For a brighter energy future,
>
>Geoff Greenfield
>NABCEP Certified Energy Practitioner
>
>THIRD SUN SOLAR & WIND POWER Ltd.
>340 West State Street
>Athens, OH 45701
>
>www.third-sun.com
>(740) 597-3111
>
>Your free subscription is supported by today's sponsor:
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-- 

Ian Woofenden <ian.woofenden at homepower.com>, Senior Editor
Home Power magazine; Subscriptions: $22.50 per year, PO Box 520, 
Ashland, OR 97520 USA
800-707-6585 (US), 541-512-0220, or download free sample issue at 
<http://www.homepower.com>

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