Merry Christmas to All!

Merry Christmas to you and all the BBS!

Merry Christmas!!!!

I'm having a good one so far. Had our string section over to track a song on the 23rd and I just finished a rough mix at about 8pm on the 25th that's sounding great. That's my idea of a great Christmas.

And... I'm having fun in Far Cry 4 on the PS4.

Happy Holidays to all!

I'm currently thrilled with my lovely new Moto 360

Very happy holidays to our extended family here on the BBS!
We spent Christmas the usual way, eating too much good food with family and close friends.

But much of our time lately is devoted to a new hardware project, with projected completion (Phase I) later in January.

Phase II (a 10KW photovoltaic array), and Phase III (deck, and attached greenhouse) are slated for late spring 2015.

Fantastic! I love it. I'll be very interested in learning more about your solar setup. Please post about it when you start going forward with it, if you're willing.

Well, more as it happens. But for now, the roof clips for mounting the solar array are slightly visible in the above photo. And the in-attic wiring was completed early on, to avoid having them tread through the attic insulation that was added afterwards.

The rear side of the house (pictured) faces exactly due South, for maximum solar gain. Having it about 5 degrees to the East might have been slightly better --> optimizing the panels' effectiveness earlier in the day, before they overheat and lose some efficiency later in the day. But due south is pretty good, and the best we could realistically achieve on the given site.

The partial wall of bricks (left) is for the inside of the future greenhouse.
And the chimney for the wood stove is green, because.. well, everyone knows a pumpkin stem is green, right?

Cheers

So what happens when the snow piles on the solar array rather than the shingles? <ducks>

-jk

Hopefully it blows off again (wind direction is favourable for this), or melts. Or covers them for a few days during the lowest sunlight times of the year.

A steeper roof pitch would have been nice -- better solar gain as well as better for keeping the snow off. But rather more expensive too, so we passed on that.

Cheers!

Must the solar array exactly match the slope of the roof and the pre-installed mounting clips?

Can the solar rack have a steeper angle than the roof, with the 'clip to solar array' attachments being progressively taller as you move up slope?

A roof of 30 to 35 degrees is ideal for solar panels. I can't tell exactly from your photo, but it doesn't look that far off.

Also, do you already know which panels and inverter you will use? I leaned towards SunPower, but eventually settled for Silevo Triex T-series, because they seemed to be a better value for money. SunPower is more efficient even, but also a 10% more expensive - besides, if you've got roof space enough, efficiency isn't all that important). With regards to the inverter, I really wanted a system that was able to address the panels individually, because we have a lot of trees over here and one dirty panel (with leaves or otherwise) means the rest of the panels on the same string will also loose about half of their capacity.

I leaned towards the Enphase system, which uses one micro-inverter underneath every panel, and directly produces AC power. The reason for this was it decentralizes the setup eases the setup even. The downside, and reason I didn't went for this system in the end, was the monitoring system uses Powerline. That in itself isn't that bad, but the Enphase Powerline monitor didn't have a serial out, and I really wanted that because I wanted to connect it to my home automation setup. This was not possible with Enphase, alas. (I guess I could have used a Kwh counter with S0 output also now I think about it...) So in the end I went with a SolarEdge system. This system uses a bit of both: Power Optimizer boxes underneath each panel which hold all the intelligence, and one "dumb" centralized inverter, with all the connections I needed.

That would create a massive snow-holding wedge, and the snow/ice would just peel the panels from the roof, in this climate anyway.

They could angle the individual panels for better gain, but our solar subcontractor has had a very bad experience doing this in the past. Something to do with high winds picking the panel and roof up off the house. Our location is particularly windy at a bad angle, so.. not in this case.

Well, for ideal solar gain, our panels would want to be 45 degrees, matching our latitude (45N). Except we get less light in the winter, as well as some snow cover, and more light in the summer, so a different angle might be better. Tough call though.

I did find a rather detailed online efficiency calculator that takes in many variables (including snow cover) and spits out the resulting value of different combinations. A steeper angle helped slightly, but not as much as I thought it might. The biggest gain there is simply from shedding snow more easily than a lower angle.


I do know, but don't remember which. There is a limited selection of them in this area, due to few (two!) suppliers, and local electrical approval requirements. But it is a single, large inverter (to be located inside our garage), and quite high on the efficiency scale. More about it when I find the documentation later.

The best deal with Solar electric power in Ontario, Canada, is something known as the "Microfit Program", whereby one can install up to 10KW of generation capability. The local utility signs a contract guaranteeing to purchse that power from us at a fixed/inflated price (per KW/hour) for the next 20 years, with the income fully tax deductible up to the cost of the system. There are several requirements to qualify, including the type of inverter and method of interconnection to the grid.

Great overview of the options, by the way!

This could be. Maybe the panels in Canada differ somewhat from the panels over here because of the difference in latitude? (to reach maximum gain?)


I've always wondered if a (slight) layer of snow on the panels and a landscape covered in it may actually benefit the energy harvest or not. Nowadays, in winter time, I've actually seen great energy harvesting values on clear days. Better than in summer even, this has to do with the panels running cooler during wintertime. Overall the total energy harvest is less of course, but this only has to do with the fact that there are fewer hours of daylight in winter during the day and obviously also a lot less sunny days in total.
It's because of this I started to wonder, at times when the landscape is completely covered in snow, and the sun is out, even if it's only a faint one, everything seems a lot brighter because of the reflection of the sun on the white surfaces everywhere. I'm very curious to see if the panels would benefit from that (provided they are not coverend underneath centimeters of snow obviously), but so far it hasn't snowed here since I've put them on top of my roof.

This is the classical approach which almost 99% of the installations use. This is not bad of course, but it is limiting in the fact that only a few strings can be used (usually 2 or 3 MPPT points). This means you get two or three series of panels on your roof. If one of those panels in one of these series starts malfunctioning or gets soiled (leaves, bird poo, ...) the energy harvest of that ENTIRE string easily halves. And you wouldn't notice until a few months later when you realize you didn't harvest as much as expected. (unless you keep a daily eye onto your energy meter )


We HAD a common system here also, but it became too expensive for the companies to keep it up, so the system got canned and all the benefit I have left is the fact that my own energy consumption is covered for the next 20 to 25 years. Also not a bad deal IMO.

You're very welcome!

Contrasting with Texas, where I have a federal tax credit on solar installation, I have zero incentives from the state, and very limited options for power buy-back.

Rant: I have hundreds of retail electric providers competing for selling me electricity, but only three willing to buy it back, and two of those are really the same company: Green Mountain and NRG. Green Mountain had the best deal, selling and buying power at the same price. If I manage to run negative, then it just goes into a virtual bank account. They'll never actually cut me a check.

Still, despite the decided lack of incentives, a few months ago, we installed solar. We have a 9kW system (36 panels, 250W peak each, and Enphase micro-inverters). I basically just wrote a really big check and now I get cheaper electricity for the next two decades.

Our house is a bit rectangular, with the longer sides facing east and west, so the solar guys decided to have an east-facing bank and a west-facing bank. This means that in the morning, the west-array is in shade and in the afternoon the east-array is in shade. Not exactly optimal, but the best they could do with my house.

What's nice about Enphase is that you get a seriously nerdy web and app experience to see how your roof is doing. They even include an optional public-facing thing (which you can disable if you're concerned with privacy). Here's my house. What that view doesn't show you is that on a cloudless bright day, I'm getting a peak of 4.5kW out of my roof, maybe half of it's rated peak power. When summer rolls around, I hope that number goes higher. Still, my monthly power usage in the winter tends to be in the 600-800kWh range, which is roughly what the solar system is putting out. In the summer, we'll get more light, and we'll be running the air conditioning more, so hopefully those continue to cancel each other out.

Curiously, Enphase uses power-line networking of some sort. You plug a box into your power mains on one end and your Ethernet on the other, and it does everything else.

More nerdy details:

Solar panels are kinda like giant batteries on your roof. Traditional systems just wire them in series, but if you've got a shadow on any one panel, it increases the resistance for the whole damn array. This is supposedly the big benefit for Enphase. Because each panel has its own inverter, a shadow on any one panel (e.g., from an exhaust vent on your roof) will cause only the one panel to produce less.

The only downside of the microinverter business is that Enphase's biggest modules only do something like 255W, versus the 350W panels that you can buy from LG and perhaps some other vendors by now. For my roof, where we've got plenty of space, it's a non-issue, but if you're very limited in your available roof and you decide to go with the bigger wattage panels, then you're not going with Enphase.

I have the same. My installation is 9.9 kWp. Now I know this is because they rate the panels at kWp, not kWh. A kWh is about 85% of a kWp, so in your case that's about 7.6 kWh your installation is able to produce. But that's ONLY at optimal conditions, meaning at the perfect azimuth angle, in plain sun all day long. This is only achievable with a solar tracker, never with an installation on a rooftop. Also, your installation is cut in half, meaning when the one 18 panels are at optimal conditions, the other 18 are not. All this combined gives you the numbers you see, even with a 9 kWp installation...


This is true, this is the big advantage of Enphase. That at the fact that you've already got AC on your roof, meaning you can use thinner cables, the fire hazard is almost non-existent, it's safe for the fire department if they ever have to hose your house in case of fire AND (the biggest benefit if you ask me) it's VERY easy to add extra panels if for some reason your energy consumption goes up in the future - kids growing up etc... : just add the extra panels to the string and that's it! (this is almost impossible with a regular central inverter, since it's always rated for a specific amount of power - and thus panels).


That's indeed one big downside that I also had an issue with, but it seems you can still run panels up to 300 kWp on them. It's not recommended, but you can do it. A bigger issue I found is that Enphase only supports panels with 60 solar cells, not the more modern panels which use 72 cells (like Panasonic) or 96 cells (like SunPower). LG actually makes a 300 watt panel using only 60 cells, but I didn't go through with it in the end, for the reasons stated in a previous post. Besides, SolarEdge did support these 96-cell panels without a problem with their Power Optimizers.

I still believe the Enphase system is best around though. They just need to update their hardware.

Thanks for all this info, guys. I so wish I could do this stuff but it's prohibitively expensive, and apparently I live in one of the absolute worst states in the country for any kind of incentives or help from the power company (virginia). I think they were talking about a total of about $34K for my system, with federal tax credits bringing it down to about $24K, and that's definitely not in the family budget right now All I'd be getting on a yearly basis would be $545 in SRECs, since apparently Virginia also has the worst SREC market.

They system they would install seems like the same one you guys were talking about, with a separate inverter for each panel and a dashboard for information about the system.

One of these days, I'm going to write up a blog post on the dollars and cents of the solar on my roof. For now, at least, the short form is that buying a solar installation looks financially a lot like buying a 20 year bond. You pay money up front and it pays out monthly. What's unusual, versus bonds, is that the monthly payments are indexed with the price of electricity. If retail electricity becomes more expensive, then the yield from your panels (in dollars) goes up.

Translation: solar panels are something of a hedge against energy cost inflation. You shouldn't think of them as a cost item, but rather as an investment (of sorts). Of course, they're an investment that's literally tied to your house, so the only way you can liquidate the investment is to sell your house.

The trick to this investment is that you need to either have a way of selling your power back, or of storing it if you don't use it. You can buy a battery storage system, but that takes that expensive solar system and makes it yet again more expensive. I suspect that you'd only ever seriously pursue battery storage if you lived off-grid, or if you had one of these cool Japanese things where you can store power in your electric car battery and then draw it back out again. And that assumes you don't actually, you know, what to drive off in the morning with a full battery...

Here, the payoff period for our $30K system should be about 6.5 years. After that, it provides us with about $5K-$6K of taxable income yearly. That is perhaps enough to offset the increased property taxes we'll be paying compared to our old, more modest property.

Hmmm... at my usage level and monthly cost for electricity, assuming I could cut my electric bill to zero with the solar panels, I could amortize that system in, ummmm, 2,125 years. (My electric bill averages about $16 per month)

tanstaafl.

Why does Enphase case about the number of cells in the panel? I though that the panels just output DC current, that an inverter, be it a per panel one like the Enphase, or a bigger one that handles a string of panels, to AC. Is there more to it?

It has to do with the voltage difference between the panels. The more cells in one panel, the higher some voltages (like Voc and Vmp) are and the current micro inverters don't really like that. Enphase has a calculator available so you can check if the panels you like are compatible with their micro-inverters. I've also noticed they started supporting *some* 72 cell panels. 96 cell panels are still a no go though. (effectively meaning you still cannot use SunPower panels with Enphase)

Power buy-back in Nevada (at least in the Reno area) is a joke. They provide you with power 'credit', so they give you free power, even though you are generating enough to have extra to sell.

And a belated Merry Christmas and Happy New Year to everybody!

Choices available to me:

- One plan will buy back power at "wholesale" rates while selling me power at "retail" rates. (Wholesale being like half the price of retail.)

- Two plans that buy and sell at the same price. It's like the meter runs forward or backward at the same rate, but if you go negative for a month, it's "banked" for the next month. If you're negative for a full year, then I think it resets to zero. I have one of these plans.

- There's an oddball "free electricity after 9pm" plan that some solar people have signed up for. The idea, broadly, is that if you've got an electric car that's drawing a ton of current at night, you might still come out ahead, even if you've got excess power being generated during the day when you're not home. (Even then, though, the marginal rate for day-time power on this plan is something like 50% higher than other plans. Seems like a gimmick to me.)

Contrast this with California, where base rates are much higher than Texas and they've got tiered pricing. (Use more than X, and your marginal rates increase.) Solar helps keep you out of the higher tier. And you've got other state incentives when you install. It's pretty much a no-brainer.

I'm on a plan like the second you describe. we never generate more power with our small system than we use, on a monthly basis, so that's fine.

Contrast with Mexico, where the billing is so complicated that not one person in a thousand understands it.

It is a tiered system, where the more you use, the higher your cost per kilowatt hour. Sounds simple, so far, but…

Billing is bi-monthly (every two months, not twice a month). If, over that two months you use less than 100 kWh, you pay only the bi-monthly connection fee, which is $17.58, except that the last time I checked was two years ago, and they average about a half-percent per two-month billing cycle for inflation, so figure it is probably about $18.66 now. If you use less than 150 kWh in the two months, the connection fee is waived, and you pay about 6.56 cents per kWh, for a maximum of $9.78. This is the "Basico" rate. Yes, it costs you less for 149 kWh than it costs for 10 kWh, but nobody uses less than 100 kWh in a month so it is a moot point. Use up to 250 kWh in the two months, and you pay the Basico rate for the first 150 kWh, then jump to the "Intermedio" rate, currently about 7.94 cents per kWh, for the remainder. Use more than 250 kWh in the two months, and you go to the "Exceso" rate, which is 25.73 cents per kWh for the overage above 250. Yes, more than three times the Intermedio rate. But wait, there's more. Once you burn a single kWh at the Exceso rate, you go back to paying the connection fee as well. And, since you managed to escalate to Exceso, even if it were just a single kWh at that rate, your Intermedio rate for the kWhs from 150--249 gets bumped up by about 37% as well.

Still too simple? Well, we're not done yet. Should you use 3,000 or more kWh during the previous 12 months, then you go into the dreaded "DAC", or "Domestic Alto Consumo" category. In DAC, every kWh you use is billed at the Exceso rate, plus you pay the connection fee. You remain in DAC until your previous 12 months total is less than 3,000 kWh. If you have a swimming pool, you will never get out of DAC.

My next door neighbor pays about $900 per two-months for her electricity. I pay about $32 per two months. I manage my electrical usage very carefully (Basico rate plus just a smidgeon of Intermedio) and I don't have a swimming pool.

I wrote a fantastically complicated spreadsheet to take care of these variables, plus a whole bunch of other variables not mentioned here: number of meters, payment in dollars vs pesos, current exchange rate, use of the air conditioning, projected inflation rate, and whether or not solar panels are installed and if so how many, etc. In my situation, I could reduce my bi-monthly electric bill down to about $6.60 cents using solar panels, and they would amortize in just 52.2 years.

Unless you are in DAC, solar panels here are a non-starter.

tanstaafl.

Thanks Doug. All this information is about to be very valuable to me. I might be needing those spreadsheets too.

I'm assuming that these rates are the same as I would get in Guadalajara?

Wow, $450 a month for electricity is nuts.

I thought I had it bad at about $325/month in the summer (AC going almost constantly + pool pump going 8-9 hours a day).

Of course, during the winter it drops down to about $80/month since the heater runs like 3 days out of the year and the pool pump is down to 5 hours a day.

We maybe run AC here 3-4 days a year; I stick with box fans after dark to the extent I can, because I'm cheap.

We run our A/C maybe 3--4 hours a year. Just on the very hottest days, we turn it on for a half hour and lie on the bed while it cools us off.

It is a heat pump system, and can also be used to heat the house. That aspect gets used perhaps 1--2 hours a year.

The average daily high temperature in Ajijic ranges, coldest month to hottest month, from 76 to 86 degrees F. At night, it gets deathly cold -- frequently the temperature drops all the way down into the mid to low 60's, at which point the locals dress up in heavy coats and parkas, and put fleece coats on their dogs. Really.

tanstaafl.

Here in the Great White North, I've never had AC at home. The new house has it, though -- required by the developer, to keep house values up, or something. We'll probably make use of it too, given the lack of trees on the lot. But all of our windows can be opened, and that will remain our primary means of cooling at night.

Meanwhile, it was -25C outside the other day. The furnace was set for 17C (but not running), and the inside was a balmy 22F. Passive solar heating courtesy of the South windows.

Can you heat your house with the AC running as a heat pump, or only with the furnace? Supposedly, "heat pump" heating is radically more energy efficient than burning gas or using resistive heat, but it doesn't work as well when the temperatures drop too low.

My mother's house has a heat pump in the reasonably large addition to her North Carolina house. It just can't keep up with very cold nights - in anything below 20F (not too usual in NC, but not too unusual, either); it runs incessantly. Those nights, she has to use the "emergency heat" setting, a space heater, or a couple fans to move heat from the gas side. The gas side is always comfy.

Perhaps the worst part is that in the rest of winter, the "heated" air blowing from the registers always feels downright cold. It doesn't blow warm enough air.

I can't speak to efficiency, though.

-jk

In this area, air-source heat pumps are apparently okay for all but the coldest 2-3 weeks of the winter. One of our new neighbours has one, which we can hear rattling away every day of the year. Thankfully, it's about 300ft away from our house.

The local vendors of such systems say they're a no-brainer for homes which don't have access to natural gas for heating. Otherwise, they're of similar operating cost (at present).

Cheers