Wanting to get into solar? Think HOT WATER 1

[OperaHouse]

Some may be feeling that they are missing the solar power bandwagon and wondering how they can do something actually useful without spending a lot of money. Batteries and grid tie make a system expensive with a long payback. Creating hot water is the most effective way to use a couple of PV solar panels since close to 100% of the power generated will be used. This assumes you are currently using a resistive hot water tank and not on demand as the rest of the civilized world. Never could get used to climbing into a shower with a 240V line.I have been heating hot water for years with excess PV for years at my camp. With as little as 800WH, we can both get a long hot shower at the end of the day. Just a couple panels totaling 400W can make a significant dent in electric use for heating. Under powering the heater assures 100% of the panels output is used. That is much greater than any battery application and much lower in cost than grid tie which isn't even allowed in some locations. Typical heat loss during the daylight hours of a well insulated tank is more than 1KWH. Solar makes up for that loss.

Most tanks have two heating elements. The top is the primary and only one operates at a time. That allows the lower resistive element to be used for solar and still have grid power backup. At 240V even a 5500W element is 10 ohms, a replacement 120V 2000W is about 7 ohms. That requires at least a 36V panel string toget any useful power. One positive is that may keep the system classified as "low Voltage". Connecting a panel directly to a resistance will result in power losses of more than half. A simple PWM circuit keeps the panel voltage at the the power point. A small capacitor bank stores the panels power in the off cycle. A panels power point voltage is the same regardless of light level. It only varies with temperature. Attaching a couple of flat pack diode bridges to the back of the panel is an easy way to get a reference voltage tracks panel temperature. I use a $5 UNO to control everything and the 490Hz PWM makes driving a FET easy. Almost any switchmode chip would work just as well.

I'm not going to argue the economics of it. Watching solar work is just plain fun and panel prices are so cheap now. Everyone has some space they can stick a few panels on. It won't freeze and none of the plumbing issues of direct solar heating. I've built several versions with just junk box parts. I have more real world details if anyone is interested.

 

[OperaHouse]

A fridge should consume a 1.5KW a day. Being generous with 12 hours of sunlight, that is a dime worth of electricity saved. Won't get a payback with that.

 

[VEBill]

"A fridge should consume a 1.5KW a day."

You mean: ...1.5 kW-hour per day ?

It's about correct, as some of the really energy efficient ones are down to "$43 a year" (assuming something like $0.10 per kW-hour).

 

[IRstuff]

Wow, I'm nowhere near $0.10/kWh

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[cranky108]

With rates like that, how is the jobs market? I would think manufacturing and other large energy users would be leaving in droves.

With our low energy rates and fair climate, we are seeing loads of server farm interests.

 

[OperaHouse]

You can tell I'm not a power guy. A friend works for lamp division, he goes ballistic when I call them light bulbs. I was being generous. Got tired of looking on gov energy star site 11CF fridge was 311KWH a year or 900WH a day. Don't know if that is average size or not. I have a 5CF chest freezer that operates as an efficient fridge. If I can get 2A into a 12V battery I will get by.

Here is my chart. Energy star appliances, heat pump water heating, CFL and LED even use a wall switch to to turn off TV. Still I am double my neighbors. The energy sucker is the hot tub. At least I do good in the summer!

 

[VEBill]

$0.31 per kWh. Ouch. Our rate (Nova Scotia) is about one-half of that. $0.14-something.

Worse than that, the Tier 1 allowance would only be sufficient for running the PVRs.

I'm not sure exactly what rate tariff is assumed for the Canadian EnerGuide labels when they provide dollar estimates for annual energy consumption, but it's a bit lower than ours. The $0.10 was a guesstimate.

My house uses simple electric baseboard heaters, but it also has about 24 sq m (!) of south facing glass (passive solar, very well insulated). My annual space heating cost is about the same as my Internet + telephone cost for a year. Not insignificant, but certainly affordable.

 

[IRstuff]

"With rates like that, how is the jobs market? I would think manufacturing and other large energy users would be leaving in droves."

Seriously? We're in SOUTHERN CALIFORNIA; beaches, sun, bikinis, did I mention sun? Only slightly cheaper than northern Calif. While large scale manufacturing is mostly gone, it's not because of the utility rates, per se, but because of labor rates. Back in the 80s and 90s Northrop moved its manufacturing to places like Georgia for the cheap labor and tax breaks the state offered to lure Northrop there. Nevertheless, housing still goes up, and there are boatloads of startups 1069 startups according to that link. Obviously, 90% of them are probably going to flame out in time, but still...

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[moltenmetal]

VE1BLL: be careful, as you need to actually break down all the fees and charges. The bills here are deliberately confusing, so I suspect the utilities in Nova Scotia are no less sophisticated in subterfuge!

Here's a breakdown of my Toronto Hydro fees:

Basic rates: this is what everyone THINKS they're paying for power:

On-peak: $0.161/kWh
Mid peak: $0.121/kWh
Off peak: $0.08/kWh

Fairly high, but not so bad compared to California!

...but then there are the fees:

transmission losses: multiply kWh used x 1.0376
transmission charges: $0.014/kWh
distribution: $0.015/kWh
regulatory: $0.005/kWh
debt retirement: $0.007/kWh
customer charge: fixed fee, works out to $0.014/kWh for me over a typical month.

That's $0.055/kWh in fees, plus the 3.76% multiplier for distribution losses

Then there's 13% HST on the whole works- yes, that's a real cost, even though it isn't hidden in the price like it is in gasoline at the pump.

That works out to roughly $0.20/kWh all in, average of on peak and off peak. That's the figure I use for comparing cost savings from efficiency or offsetting with rooftop generation etc. Lots of options pay back at $0.20/kWh. What depresses me is that the microFIT contracts for solar PV pay people $0.50 or so (it was previously $0.80) per kWh for all the power they generate from their rooftops, even if not a single electron in fact leaves their houses and enters the grid...those FIT programs should only be for net excess power generated.

Contrary to popular belief, there hasn't been a mass exodus of manufacturing in Ontario due to increased power pricing. Manufacturing has been in decline locally, but it's resulted almost entirely from industry consolidation and offshoring- and that has helped us avoid installing another CANDU reactor plant which would cost tens of billions of dollars that we could otherwise invest in transit etc. As a society we prefer (now) to import cheap goods of all kinds and let others obtain all the benefits of manufacturing them. Trade protectionism is out of vogue in the developed world for manufactured goods. Agricultural goods produced by the very poorest workers in the world (in sub-Saharan Africa) are still subject to crushing duties here though- I guess farmers still have quite a bit of lobbying power, and unlike China or Korea etc., the sub Saharan countries lack the clout to fight back.

 

[VEBill]

NS is simpler.
$10.83 / month fee 'base charge'
$0.14947 / kWh
Only 5% GST (the provincial HST is rebated for some reason)

That's it.

I've never bothered with ToD since my heating fraction is low, it would work against me.

 

[moltenmetal]

Wow, that is uncharacteristically plain and simple! What are those guys thinking? People might actually understand their bills that way!

Time of day metering is mandatory here. The great thing is that if you sign up for their Peaksaver program (giving them the power to turn your air conditioner off for short periods during the peak, actually saving me money in the process- we only really NEED it for sleeping in July and August), they give you a digital power monitor which interfaces with the smart meter. Easy way to understand what's drawing power in your home, and when.