[RE-wrenches] PV-direct electric water heating

[Dave Click]

At SPI last year there was at least one company offering this, and 
there's another company from Tallahassee also looking into it: 
www.usa-eds.com

I'm not an expert by any means but I think that even 120F doesn't kill 
legionella-- you need to get to 140F. And even if you do 140F, I imagine 
you could still have it in the bottom of the tank (if it's electric).

A few years ago, a Solar Decathlon team used some kind of ionization to 
combat it, I believe using something intended for hospitals.

DKC

On 2013/5/14 8:39, Steven Lawrence wrote:
> Luke,
> Most tankless hot water heaters can't accept pre-heated water.  Some of
> them can, but even still these have a minimum heat input into the
> water.  You may run into a situation where you have 105F water into the
> tankless and the thing won't fire up due to safety reasons (can't put
> out 130F or something similar like that).  And the issue with 105F is
> you start exposing yourself to the potential of getting Legionnaires'
> disease.
> -Steven
>
>
>
>     Hi Wrenches,
>     Now that the cost of modules has come down so much, has anyone out
>     there experimented with solar electric water heating? As in: direct
>     connecting a short series string of PV modules to a tank -style
>     electric water heater with an element of an appropriate voltage and
>     wattage rating??
>
>     A off-grid customer of mine who is also an electrical engineer has a
>     situation that seems ideal for trying this idea out: he has a
>     gas-fired tankless water heater and a water source that is very cold
>     year-round. The idea is to take a 30 or 40 gal electric tank heater,
>     switch out one of the the 240V elements to something like a 96VDC,
>     1000W element (difficult to find, but available), and direct connect
>     3 or 4 60-cell modules in series (with a disconnect and high-limit
>     control of course). The tank would then serve to preheat the cold
>     feed to the tankless heater. We think we can get a decent daily
>     temperature rise with this setup. Probably not enough to heat the
>     tank to a normal DHW temperature, but certainly enough to offset a
>     good deal of propane consumption, and all for what I predict will be
>     considerably less cost than a small solar thermal system.
>
>     Has anyone tried this? I'd appreciate any insights or opinions.
>
>
>     Thanks
>     -Luke Christy
>
>
>
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