New guy here

Hi, I just found this site & don't know a "reply" from a "quick reply," but...

I'm on the verge of installing DSHW with a flat plate collector feeding into an evacuated tube collector using a small 12VDC PV panel to power the controller & pumps - BUT, I've just discovered Guy Marsden's site & now have thoughts of installing a larger grid-intertied PV system. (in Vermont we get about twice as much for our feed-in as we pay the grid for our feed-out). Enphase produces micro-inverters that provide 240VAC @ the panel & allow for gradual, integral, mix-&-match growth.

So then (2 days ago!) I started wondering about avoiding all the plumbing, worries & maintenance of solar water & just using PV to heat our super-insulated tank, and I started in again clicking away at the Internet. Then I found you guys. I'm wondering if you have any comments or links to share on this point. (I shudder to think about discarding all the plans, drawings, & other info I've collected to this point....)

Background: Our highest electrical use in past two years is 10 KWH/day averaged over a month; 7 is our yearly daily avg. We built our own super-insulated timber-frame house with a wall of south-facing windows. We heat only with wood (masonry & backup cast iron stoves); heat our water from the wood stoves Oct - April; cook on wood cookstove late Sept. - early May. Composting toilet, wringer washer & clothes lines. Only two of us in house; one shared shower/day; low hot water use & heat loss. I do all the HVAC & carpentry work - sometimes with professional help.

Thanks in advance for any replies.

[Xringer]

Hi Gerg, and welcome!

If your goal is to heat hot water for and not heat your home,
it might be a good idea to look at using PV into HW heating elements.
In my case, I want to reduce my oil use. I guess you want to cut back on cutting wood.

With that 2x$ payback for your extra PV net-metered power, EnPhase looks
like a great way to start up a system and grow it over time.

If you installed a large PV array and used a timer controlled HW heater
and/or a light load HW heater, it seems like you might get to break-even
a bit faster than you might think..

For a lot of reasons, I'm pretty sure that energy costs are not going to remain stable very long.

If someday, you do own a big PV array, you might want to look into
heating and cooling with a Mini-split ASHP.
http://ecorenovator.org/forum/projec...l-project.html
They don't use a lot of power and the work pretty well in cold weather.
It's perfect for mild spring weather too. My house is at 72 right now
and we are heating the house for about 3.5 kwh per day (70 cents) this month.
Is 70 cents a day cheaper than chainsaw gas and a sore back?

Cheers,
Rich

Thanks for your comments, Rich. Do you know where I could look into the electric hot water possibility some more? The timer could really help because I could sell @ 30 cents/kWh during sunlight & heat @ 16 cents/kWh afterwards.

I'll suggest th@ Sanyo device to others, but our timber frame has no interior walls & being in the woods in northern VT cooling isn't a big issue here.

[Xringer]

Here's one good place to look.. BFRL: Solar Photovoltaic Hot Water System

Click on publications to read the study papers.
I'm pretty sure they are doing some pvwater down in Australia, but finding
their studies might be a task..

Cooling with the Sanyo isn't a big issue to me either (for my wife it is).
We got the Sanyo primarily for heating. To cut back on burning heating oil.
We just got an oil fill, $484 and I'm hoping it's going to last until Dec..

One thing I do like about using the AC, it's got washable filters.
During the spring pollen season (now), we can button up the house
and run the AC for peanuts and I can avoid using eye drops every few hours!


It was 38F when I got up this morning. Weather Station History : Weather Underground
It was about 66 in the bedroom (my wife likes to sleep cool), but I had left
the Sanyo at 68 last night, so we had the main living area up to 70-72 by the time I had my oatmeal.

I have to say, I don't mind heating the house during this kind of weather..
Being warm is great for my old bones. And for 70 cents a day.?. I can live with that.

Thanks for the link. Actually, that was the only place I'd found any info & was hoping for more, oh well. I guess it's probably not such a great idea then....

We're lucky to not have a propane or oil tank, & there's no gas lines out here (we don't use TV, but there's no cable either). The idea of the AC as a filter is a great one. My son & grandsons in eastern VT all have allergies. I'll pass this tip along.

We've gotten 8+" of snow since yesterday morning & it's still coming down. Rt. 2 is closed w/ jackknifed trucks & many cars of the rd. But our little woodstove downstairs & our cookstove up here are keeping the place cozy. We're looking forward to our new PV & solar hot water systems.

[Xringer]

It's not a 'great' idea, unless you can buy your PV panels at a good price.
If you read the conclusions of one of those papers,
they say $1 a watt is where it's going to be cost effective for homeowners.

But, as time goes by and fuel cost goes up, I think the $2 per-watt era is upon us..

My experience with solar thermal hot water was pretty good,
but I expected the equipment to last at least 20 years before leaking.
It seems the water here in Woburn is hard on plumbing.
Both the storage tank (84 gallon) and heat-exchanger started to developed leaks after 10 to 15 years IIRC.

I suspect that a PV array will still work pretty well after 30 years.
(Or, until I'm 94)..

The house was built in 1956 and I had replaced all the copper plumbing
by the early 1980s. It was all paper thin and would leak if you looked at it wrong..

Anyways, I don't think PVHW is for everybody. It's not near as efficient
as regular solar HW, but I'm not sure about the hardware cost.
I've seen some lately that aren't that cheap..
Sunward Solar Hot Water System - Solar Hot Water Details and Pricing

8+ " of snow?? Wow! We are lucky here.. Just cold and wet..

Cheers,
Rich

[mrd]

I imagine the initial investment on the thermal system is much lower than the PV system. The PV has potential for greater ROI, but that's assuming the equipment lasts a loong time. It's more risky in that something may happen before you start getting money out of it.. like damage to the equipment, or you move for whatever reason.

I dont expect prices for thermal equipment will change much in the new few decades, but PV prices will definitely decline. So there's also a difference in the change in worth of the equipment over time.

Either system is going to require at least minimal maintenance, e.g. cleaning the glass, clearing off snow. If hail is at all a concern, compare the toughness of the panels you are considering. And how will the installation of either affect your homeowner's insurance?

However, you're currently using wood to heat your hot water.. that can't cost much. I assume you'd have an electric hot water heater connected to the PV system? You can find expected kWh usage for that easily. Compare that to the kWh you expect to get from the PV system. Those numbers should also be available, just be sure they are for your specific latitude and take into account the angle they will be installed and any shading they will receive throughout the day/year.

Our friends 15 mi. east of us aren't in a protected valley like we are; they got 18". But it stopped 2 hrs. ago & sun is out. Will be up to 40 or so tomorrow. All will be but a memory.

MRD: Thanks for the list of considerations. Sure never considered home insurance; we'll hafta look into that. Tying up to the grid & skipping the big battery bank while using microinverters (allowing for seamless growth) removes some of big drawbacks, as far as I'm concerned.

The wood comes off our 17 acres of forest with the help of a John Deere 420 crawler. But I'm exactly Xringer's age & am looking forward backing off on some of that work someday. I'm hoping that some extra hot water for a heated floor downstairs might contribute toward that goal. Our footprint is 40' X 40' but we've no interior walls, so it's pretty easy to heat it.

All of our tanks are used throw-aways that I test, strip, clean, insulate - pressure tank, too. Roof is pitched only enough to shed water - we use the snow to boost our already R-55 rating, & the wife doesn't like snow clobbering her perimeter gardens.... So the panels will all be mounted south-facing & angled for best average. (We've no bldg., electrical, or plumbing codes besides septic, & we have a composting toilet & gray water field.) I've left the top heating element in our final-feed hot water tank so's we can "cheat" in a pinch.

As you suggest, the falling prices & increased efficiencies of PV probably suggests not over-bldg. & instead adding on as need & value increase. I'll look into that further. I can always provide extra mounting area on the roof while we're up there since extending sideways will be so easy. (It's a 48' X 48', 65mil fully-adhered EPDM surface that we sometimes hang out on if it's not too hot. Barb likes lying up there watching the bats gorge themselves in the evening.)

I'd be willing to send a virtual beer to anyone who can find a solar calculator that'll take into consideration a two-stepped electric utility bill & the fact that we get 30 cents/kWh for what we contribute.

[Xringer]

My hot water comes from a coil in our heating boiler.
I've been studying the heat loss by using a 250 watt electric heater,

http://ecorenovator.org/forum/applia...ad-heater.html

Right now, I'm using a timer that turns on and then off in 30 minute cycles
for 12 hours during the day. (6 hours total for 1.5 kWh /5118 BTU a day).

By loosely keeping track of our hot water usage verses the amount of time
the oil burner runs, I'm starting to see that a mere 250 watts is going to save us some oil,
but the amount is going to vary a lot. Like when the dishwasher comes on etc.

I'm not sure, but I think the on-and-off cycle of the timer might not allow
the heater to be as effective as it could be, if left on.

So, I'm thinking of using a 600w lamp dimmer to preset the heater for
100 to 250 watts during 6 hour (daylight) cycles to find out how different
amounts of E-heat into the mix will affect our oil usage.
I'm kind of wishing I had a 500 watt heating pad to play with..

Sorry I've been out of the loop: parents visiting from OH, daughter & granddaughter visiting from Newfoundland. I was following your heater exploits before I hopped in & disrupted everything. I'm gonna abandon this thread & go back to following the conversation. Thanks you guys for all your help.

Greg