Designing and building a solar power station

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Designing and building a solar power station

#1  Postby The_Metatron » Aug 04, 2017 8:57 pm

In the last twenty four hours, it's been hotter than hell at my house. The high for the day was 40 C in my back yard. During that 24 hours, I used 40 kWh of energy to cool my house, with my heat pump/air conditioner set to 24 C. That's not terribly expensive here, electricity is a little less than $0.06 per kWh. So, electricity cost me $2.50 for that day. That's pretty reasonable.

But holy shit, the sun has been shining here, uninterrupted by rain for at least the last six weeks, and that is likely to continue for the next six to eight weeks. This is as I remember from living in the Willamette valley: typical Pacific northwest rain over the winter, but glorious summers.

After doing a little preliminary reading, it seems that for my locale, a fifteen year amortization of the cost of a solar power system is normal. But, that fifteen year period is based on commercial installation funded by commercial loans (such as a home equity line of credit, or HELOC). It's also based on installing a 2 kW system. I think I can improve that amortization curve and realize payback sooner than fifteen years.

My goal is to produce all of the electrical energy I need. Getting from here to there is no simple thing. But, I don't think it involves any particularly difficult or unsolvable problems, either.
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Re: Designing and building a solar power station

#2  Postby tuco » Aug 04, 2017 9:03 pm

You could consider doing actual measurements in your location. This way you will be able to calculate return on investment quite precisely. Over here companies who offer solar systems for home use also offer such service, along with solar calculators. If I had money to invest, this would be on top of my priority list.
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Re: Designing and building a solar power station

#3  Postby The_Metatron » Aug 04, 2017 9:13 pm

How much energy do I need?

As I just wrote, I used 40 kWh in the last 24 hours, running my house in its current configuration, operating my cooling system, doing a load of dishes in the dishwasher, a couple loads of laundry (hang dried on the line), typical kitchen appliance usage, and typical home electronics (computers, television, etc) usage.

Give or take a few kilowatt-hours, that should describe my peak demand. Though another question comes to mind: Does it cost me more to cool the house when it's 40C, or to heat it when it's approaching freezing? I better look at that a little closer. Even when it's crazy hot like it has been the last few days (and is likely to be for the next six weeks), it cools down to 20C or 21C at night. In the summer then, I can simply ventilate the house with outside air for night time cooling, which brings internal room temperatures to below my environmental control system cooling setpoint of 25C.

But, I better have a closer look at heating operation in the winter. Of course, I don't heat it to 25C. I heat to 20C.

Looking at the two exterior temperature limits I am likely to see (0C to 40C), my heating setpoint of 20C is farther away from the likely coldest winter temperature than my cooling setpoint of 25C is from the likely hottest summer day of 40C. I don't know how that's going to factor into defining my requirements.

I think I should see what the power utility company will tell me about the energy usage at my house in previous years.
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Re: Designing and building a solar power station

#4  Postby The_Metatron » Aug 04, 2017 9:15 pm

tuco wrote:You could consider doing actual measurements in your location. This way you will be able to calculate return on investment quite precisely. Over here companies who offer solar systems for home use also offer such service, along with solar calculators. If I had money to invest, this would be on top of my priority list.

Yes, some sort of site survey is certainly required. That can very accurately quantify how much energy I can collect.

On what I'm going to have to guess is my energy requirements. I haven't lived in this house long enough to have my own records. Time to call the power company...
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Re: Designing and building a solar power station

#5  Postby Macdoc » Aug 04, 2017 9:28 pm

Your first goal is to improve your insulation ....there are infrared meters you can get to identify areas needing better insulation including windows where you can change the glass to better stuff.

Panels are cheap, BUT you have to go off grid otherwise you are into feed-in tarrifs. WIth panel costs so low and you doing install I'd bet 5-7 years is achievable once you button up the house.
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Re: Designing and building a solar power station

#6  Postby tuco » Aug 04, 2017 9:38 pm

The_Metatron wrote:
tuco wrote:You could consider doing actual measurements in your location. This way you will be able to calculate return on investment quite precisely. Over here companies who offer solar systems for home use also offer such service, along with solar calculators. If I had money to invest, this would be on top of my priority list.

Yes, some sort of site survey is certainly required. That can very accurately quantify how much energy I can collect.

On what I'm going to have to guess is my energy requirements. I haven't lived in this house long enough to have my own records. Time to call the power company...


I was wondering where your electricity bills are :)

As for insulation. I think its very good way to save energy, however, efficiency of various measures (windows, wall, doors, roof etc) obviously varies and imo some research before investing is in order. I've done it, only research in order to qualify for subsidies .., myself some time ago, that is why I mention it.
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Re: Designing and building a solar power station

#7  Postby The_Metatron » Aug 04, 2017 9:41 pm

From last August to now, my house used 18 mWh of energy. A little over a thousand bucks' worth. There was only one old man living here, though. So, my family of four is certain to use more energy than he did.

On the other hand, I replaced three to four thousand watts worth of lighting with LED lighting that uses a tenth of that amount of power. I replaced the oven/range with a shiny new one with two ovens (one is quite small), and the hob is an induction hob. So, we are using probably half the energy Carl did with his old resistively heated stovetop.

My next upgrade, before the solar system comes online, should be my electric water heater. It's a standard resistive heated water heater. The new hybrid resistive/heat pump water heaters use 75% as much energy. There isn't much I can do about my clothes dryer except to not use it. Likewise with the clothes washer, we don't wash with hot water unless it's really necessary. It hasn't been, yet.
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Re: Designing and building a solar power station

#8  Postby The_Metatron » Aug 04, 2017 9:49 pm

Macdoc wrote:Your first goal is to improve your insulation ....there are infrared meters you can get to identify areas needing better insulation including windows where you can change the glass to better stuff.

Panels are cheap, BUT you have to go off grid otherwise you are into feed-in tarrifs. WIth panel costs so low and you doing install I'd bet 5-7 years is achievable once you button up the house.

Ahh, a good point I hadn't considered. Not much I can do about the walls. The windows are pretty nice. But, I can get a dude in here to double the thickness of the attic insulation, with some ease and not much cost. I better get that one on the calendar, too.

As for grid connected or not, I've studied that problem. Feed-in tariffs are appropriate. Someone has to pay for all that infrastructure, and I get that.

What isn't so easy from an energy perspective, is network power balancing. If me, and many like me, show up with unpredictable and uncontrollable power generation, the network operators have to account for that in balancing the power in the grid. This isn't always so easy. It depends mightily on the sources of power.

Our power here is hydroelectric. Wow, is a hydroelectric power grid an easy thing to balance. It's as simple as adjusting the intake valves to the turbines, and it can be done immediately. Coal and nuclear plants can't change their power output significantly or quickly. They don't have volume controls. Power balancing in networks fed by those types of plants is much more complex, it involves changing the frequency of generated power, and can actually cost more energy to balance than is input into the grid from distributed, uncontrolled generation. I'm good to go then, from the perspective of effects to the power grid.
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Re: Designing and building a solar power station

#9  Postby pelfdaddy » Aug 05, 2017 3:10 am

There is something you can do about the walls.

There are companies equipped to remove strategic sections of your siding, drill holes in the outside cladding, and blow cellulose fibers into the voids. The material is a wonderful insulator, and the return is usually startling. If you have living space above your garage, don't forget to fill in the garage ceiling as well, and be sure to apply chunks of blanket insulation to the little square exterior spaces between the top plate of your basement (or crawlspace, which is popular in your part of the world) and main floor decking.

And get some curtains with white thermal backing that faces out.
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Re: Designing and building a solar power station

#10  Postby The_Metatron » Aug 29, 2017 6:54 pm

I was thinking about a 20 kW solar plant. That's 100 square meters of panels, maybe a bit more. That's a lot of damned power.


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Re: Designing and building a solar power station

#11  Postby The_Metatron » Aug 29, 2017 6:59 pm

On the other hand, I rarely pull that kind of power. Maybe, if I were running the heat pump along with the oven and water heater. What I have to decide early on is if I'm going to rely on a grid connection for peak demands. I think so, at first.

Later, I can add battery banks. I have the shelter for them, and the inverter equipment, already attached to my garage. I'll want to finish that shed, pour a floor, insulate it, etc. I will have to pull heavier cable through the conduit between the buildings to feed the house from the garage.


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Re: Designing and building a solar power station

#12  Postby The_Metatron » Aug 29, 2017 7:02 pm

Here I am, making tea and charging my iPhone off-grid:

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Let the sun do some goddamned work for a change.


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Re: Designing and building a solar power station

#13  Postby tuco » Aug 29, 2017 7:33 pm

20 kW is lot of power indeed. For homeowners here from 3-6 kW is usual. What's the return of investment on it?
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Re: Designing and building a solar power station

#14  Postby laklak » Aug 29, 2017 7:35 pm

I think theropod had a thread where he discussed his off-grid setup in detail. Was a few years ago.
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Re: Designing and building a solar power station

#15  Postby Macdoc » Aug 29, 2017 7:37 pm

Depends both on his cost of power ( so savings )
and the feed in tarrif ....

ROI off grid is likely much higher than feed in based.
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Re: Designing and building a solar power station

#16  Postby theropod » Aug 29, 2017 8:29 pm

Bookmarking. Been doing yard work for two days straight following our trip out west, and too spent to think clearly. Jesse faces a whole different set of issues than our off grid system even with similarities. I have input, but it can wait until I rehydrate and chill.

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Re: Designing and building a solar power station

#17  Postby Adco » Aug 30, 2017 9:07 am

The_Metatron wrote:My next upgrade, before the solar system comes online, should be my electric water heater. It's a standard resistive heated water heater. The new hybrid resistive/heat pump water heaters use 75% as much energy. There isn't much I can do about my clothes dryer except to not use it. Likewise with the clothes washer, we don't wash with hot water unless it's really necessary. It hasn't been, yet.

I installed a timer for our geyser. I turn it on from 5-7am and then from 5-7pm. I saw a drop of R400 (about 10%) off our bill the next month and it has been down since, about three years ago. Also try turning the geyser temperature down if you can. Even a 5 degC will make a difference.

Another thing to try is double glazing. A lot of heat is lost through windows. The glass is a fairly good conductor of heat and an air gap between two panes helps buffer that transfer of energy. I am going to try that at my house. Our bedroom is freezing in the winter and our windows are perfect for adding another sheet of glass separated by a 5mm strip of wood. Cheap enough to experiment with. Only R650 for a 1.8m x 1.4m sheet of 3mm glass.

One more place to insulate is the roof cavity. Apparently that stops heat transfer in the summer.
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Re: Designing and building a solar power station

#18  Postby The_Metatron » Aug 31, 2017 12:47 am

Adco wrote:
The_Metatron wrote:My next upgrade, before the solar system comes online, should be my electric water heater. It's a standard resistive heated water heater. The new hybrid resistive/heat pump water heaters use 75% as much energy. There isn't much I can do about my clothes dryer except to not use it. Likewise with the clothes washer, we don't wash with hot water unless it's really necessary. It hasn't been, yet.

I installed a timer for our geyser. I turn it on from 5-7am and then from 5-7pm. I saw a drop of R400 (about 10%) off our bill the next month and it has been down since, about three years ago. Also try turning the geyser temperature down if you can. Even a 5 degC will make a difference.

Another thing to try is double glazing. A lot of heat is lost through windows. The glass is a fairly good conductor of heat and an air gap between two panes helps buffer that transfer of energy. I am going to try that at my house. Our bedroom is freezing in the winter and our windows are perfect for adding another sheet of glass separated by a 5mm strip of wood. Cheap enough to experiment with. Only R650 for a 1.8m x 1.4m sheet of 3mm glass.

One more place to insulate is the roof cavity. Apparently that stops heat transfer in the summer.

The next water heater will be smart and also a heat pump hybrid. Adds to the expense, but it pays for itself in 2.5 years in electricity savings. I have a useful location for a heat pump hybrid water heater, in that my upright deep freezer is in that same room. Lucky for me. Suck the heat out of the crap that needs to be frozen, then vent it into that utility room so the water heater can use it to heat my water.

The windows are all nice double pane low emissivity type, so that's not a worry. But there's plenty of room up in that attic for twice the blown in fiberglass than exists up there. We'll be fixing that before winter.
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Re: Designing and building a solar power station

#19  Postby The_Metatron » Aug 31, 2017 3:14 am

The_Metatron wrote:Here I am, making tea and charging my iPhone off-grid:

Image

Let the sun do some goddamned work for a change.

As pictured there, that little array is lying flat. Still, enough for the phone to report it is accepting charge. I was surprised today that I got that same indication on my iPhone today, even while it was fairly overcast. I don't know how accurate that little charging indicator is. But, the title charger that came with my iPhone is a 5 watt charger. 5 volts (+-0.25V) at a maximum of 1 ampere. So, that phone charges on something less than 1 ampere of current. How much less would be useful to know.

From the perspective of solar energy, I'm really interested in how much energy (kWh) the goddamned thing uses. The iPhone 6 battery is 1810 mAh capacity. Judging from their published specifications, coupled with my own observed use patterns, I'm estimating I burn through half that battery in a day. I've used nearly all of it in a day (during the solar eclipse of 2017 incident), but that isn't normal.

For routine use then, I'm going to estimate that my phone uses around half it's battery capacity, around 1000 mAh, every day. I can easily convert that value to energy by multiplying the current in that unit by the applied voltage, which is 5 volts, to get 5000 mWh, or 5 Wh, of energy to run my phone for a typical day. Not a lot of energy, really.

Some guys at Oracle tested the charge required to recharge a dead iPhone 6: 10.5 Wh, and it took 1 hour and 48 minutes. That agrees fairly well with my estimate of 5 Wh to recharge mine from about half discharged. Judging from their charge times from dead to full charge, It looks like the charge rate averages out to about 5.8 Wh/h or simply 5.8 W for 1.8 hours. It certainly isn't linear, though.

The maximum power from any one of the three ports on my new RavPower solar array is 2.4 amps at 5 volts, or 12 watts, with a maximum output power of 24 watts, shared across those three ports evenly if they are all in use. So, I should be able to match the performance the Oracle guys measured.

Phones don't take much power. I spent about 72 bucks on it. My phone will cost me about 31 cents to use every year. This solar panel will pay for itself in about 230 years.
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Re: Designing and building a solar power station

#20  Postby The_Metatron » Aug 31, 2017 4:15 am

More about that RAVPower solar panel...

It's cool as shit to be able to get usable energy directly from free sunlight. My iPhone isn't very thirsty, though. I found that the iPhone charging indicator shows charging is happening when the solar panel isn't all that well illuminated. Cool.

Charging my iPad Pro is a little different. It wants more current than the iPhone does. Not sure how much more current, I haven't looked for it. But, more. I found that the iPad wanted that solar panel in full sunlight before it will indicate that it is charging. The thing about that charging indication is that the device does need to be booted to view it. What I mean to say is that I was able to get my iPad to report that it was getting a charge from my solar panel, while I was actively using it.

Usage patterns may be that it isn't entirely convenient to sit outside while my iPad or iPhone recharges in the sun. In just a day or two of using that solar panel, I can see that I need the ability to store energy I collect for later use. Or, perhaps for higher peak power demands than my solar panel can produce.

The answer to that is a power tank. That came in the post today, and it came fully charged. It can deliver 26.8 Ah. That's quite a feat, considering the size of the thing is 17 x 8 x 2 cm.

In stressed conditions (no mains power), I will use my solar panel to keep this battery fully charged, then charge my USB devices from it. In emergency conditions, I'd charge that battery plus at least one other USB device as long as I had sun shining, the idea being to collect and store every damned watt hour I can get.

I didn't buy an economical way to operate my phones. I bought security. I can now power my phones and tablets indefinitely and independently of mains power. I am not going to be without comms. That's what I bought for my 72 bucks.
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