[Greenbuilding] is it ever sensible to use PV to heat water?

[Reuben Deumling]

On Fri, Mar 23, 2012 at 11:47 AM, Reuben Deumling <9watts at gmail.com> wrote:

>
>
> On Fri, Mar 23, 2012 at 11:32 AM, Steven Tjiang <steve at tjiang.org> wrote:
>
>> I understand the grid issues but in my opinion, we are no where near
>> having enough PV to have those problems.
>>
> I see this as a dynamic problem that exists/manifests itself at all
scales. I am disinclined to welcome much less celebrate any end use that
relies on electricity to heat something (water, air, food, etc.) in a
climate zone that, like mine, experiences a coincidence of winter peak and
low solar insolation. We are trying to move away from fossil fuels as
quickly as possible. To my knowledge these extra electric end use devices
(e.g. Holladay's HPWH) are not flexible or resilient when it comes to
future adaptability to a no fossil fuels world. They are voracious
kW-eaters during the precise period when the championed renewable 'fuel' is
unavailable. When we get serious about phasing out fossil fuels, we're
going to find ourselves scaling back to the essential services for which
electricity is uniquely suited (motors, computers, refrigeration, lights
perhaps). Electric water heating strikes me as an end use that would not
make the top ten.

Micro-economic calculations aside, we should (continue to) welcome modular,
stand-alone, simple technologies that can provide the service of domestic
hot water and that don't rely on the grid. I see the grid as a huge future
liability, and would not personally want to increase my dependence on it
for tasks that can readily and inexpensively be met with technologies that
are not grid connected. I already mentioned my favorite one above: solar
thermal + wood for year round fossil fuel free water heating. And let's not
forget the pilot-light heated DHW as an option. At 35 therms of natural
gas/yr it is most assuredly reliant on a fossil fuel, but it should be a
contender if we're talking about HPWH and a grid that in this country at
least is still majority coal.


> when we get there.....that's a good problem to have (and solve).
>>
> I don't see this problem as one we will find easier to solve once we've
had ten or twenty years to take Holladay's advice. The rising tide can't be
counted on to float stranded assets.
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