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Building my own solar power system

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Re: Building my own solar power system

#341
post #176

Earlier quoted context omitted.

What is your recovery plan in the event of a hurricane? I'm not fond of high electric rates, but in addition to generation those rates amortize and distribute the cost of storm recovery. A home or business with grid-tied solar pays interconnect fees for the option to get paid back a little for excess generation, and the option to decide to switch back to 100% grid power if a storm damages the on-site panels.

> those rates amortize and distribute the cost of storm recovery Not exactly when it is a farm out there away from a town. My experience is from a different era (90s) and a different kind of farm, but I spent a bunch of summers in one, which had power outages whenever the monsoons picked up. The trouble was that there was a single line feeding the farm from about 6km away, so if that went down a single farmowner comp…

I would have thought an isolated farm would have had propane on site - likely more than one tank.

I don’t worry about outages much in my current home because the main line to ~1000 houses goes right past me, and I’m fed straight from it. If I’m out, it’s a very high priority line. Worst ever was about two days. It helps that our worst storms are usually in spring, so weather is mild.

Re: Building my own solar power system

#342
post #144

I’ve been running a solar microgrid on my coffee farm for the last 7years. We started with a few golf cart batteries and 4 panels, these days we’re powering 4 houses, 7 cabins, water extraction, treatment, and RO processing, campus-wide fiber network and switches, path lighting, security systems, and a small server rack. We’re running 6 inverters on our primary system in a three phase configuration, 35kw of panels an…

Naive question, why run inverters? Wouldn't it be more efficient to run direct DC appliances? We have a building on our farm without power and it'd be ideal to be able to charge batteries and run lights at night It seems to me that we would have to upsize batteries in order to make up for the loss in converting to AC

I'm not an electrical specialist but there are three major reasons I'm aware of that AC "won" at normal household/commercial power levels:

1. Switching. If you go look at your favorite part supplier you can find a bunch of switches that are rated to switch 250 volts AC and pass 16 amps, enough for basically any standard household outlet anywhere in the world. Those same switches are only rated for 24 volts DC. Why? Because of arcing. AC voltage passes through zero twice a cycle, which means that any arc that may be formed will self-extinguish within a hundredth of a second. DC doesn't do that, so the arc potential has to be limited either by reducing the voltage or increasing the size/complexity/cost of the switch/relay/contactor itself. This also applies to any connectors that may be unplugged under power like wall outlets. If you want to do the same amount of work with DC as you do with AC you basically get the choice between doing it at lower voltage with thick expensive wires or doing it at higher voltage with expensive switches, relays, outlets, etc.

2. Motors. Synchronous AC motors are EVERYWHERE. They're simple, cheap, efficient, and as long as they're not overloaded they run at a consistent speed determined by the number of magnetic poles in the motor and the AC frequency. If you have an appliance or power tool that runs on mains power and does not offer motor speed control (or only offers two or three speed settings) it's likely one of these. Native DC motors are also cheap and simple but but have very different performance characteristics, no native mechanism for precise speed control, and flow current through the rotor which requires brushed contacts that wear out over time. "Brushless DC" motors are actually AC motors paired with a controller which is more or less a DC->AC inverter, adding cost and complexity that may not be otherwise necessary or beneficial to the application.

3. Voltage conversion. AC can use simple wound transformers to efficiently trade voltage for current or vice versa using nothing but wire and metal. You might have used or even built one in a middle-school era science class. DC voltage conversion on the other hand, the simple methods are inefficient and the efficient methods require high-frequency electronics which only became inexpensive enough to go mainstream in the last 50ish years.

None of these are insurmountable problems of course, especially these days when switch-mode power supplies, inverters, VFDs, etc. are cheaper than ever but they still make things more complicated and require going against in some cases multiple lifetimes of industry inertia to purchase equipment produced in much lower volumes which means higher costs, and especially for home applications where size and weight are not the biggest deals it can often be easier/cheaper to just run a larger solar/battery setup to counteract the efficiency losses.

In the RV and boat worlds where size and weight matter you'll find a lot more DC appliances, but those are also generally smaller capacity than a household equivalent.

Re: Building my own solar power system

#343
post #234

Earlier quoted context omitted.

I'm not sure government incentives allow the free market to do its work, then. Why would you think it would?

government incentives help to reduce the externalities You seem to think that two companies selling product A will rather sell 50 for $10 per unit profit than 100 for $9 per unit profit because it's easier. I mean, it's a view, sure.

> You seem to think that two companies selling product A will rather sell 50 for $10 per unit profit than 100 for $9 per unit profit because it's easier.

If the numbers are closer, then that's exactly what happens.

Would you rather sell 50 units for $19 per unit or 100 for $10 per unit? Option 1 gives you way less overhead and headache with cheap-o customers.

Re: Building my own solar power system

#344

Earlier quoted context omitted.

> It’s strange to me that people in rural areas pay for electricity. It makes no economic sense, at least here in the Caribbean. This comment was very confusing until I read the second sentence. Electricity prices in the Caribbean are very high, and I can only imagine that rural areas are even worse. Where I’m at in the United States a typical electric rate is around $0.10/kWh. Paying that nominal amount and avoiding…

I’m in a mountain town in BC Canada and pay $0.13/kWh. My 7.8kW solar system cost me $0 out of pocket after incentives and an interest free loan. It’s making ~$1000 per year of electricity, so we’ll just put that onto the loan for the next 8 years instead of paying it to the power company. Then for ~25 years after that it will make me $1000/year. Free money. (The price of electricity is already pre-approved to increa…

Why pay off an interest free loan?

Re: Building my own solar power system

#345

Earlier quoted context omitted.

magnitude less power from PV than in the summer magnitude more power from PV than in the winter That is a tautology.

However, the implied meaning is significant. This site is full of engineers who, if they're good, invest a lot of time into understanding the implied meaning of what's said.

There is no implied meaning, you cannot derive PV building intend from it.

Re: Building my own solar power system

#346
post #252

Earlier quoted context omitted.

Naive question, why run inverters? Wouldn't it be more efficient to run direct DC appliances? We have a building on our farm without power and it'd be ideal to be able to charge batteries and run lights at night It seems to me that we would have to upsize batteries in order to make up for the loss in converting to AC

Not who you're asking. I really don't see why we're still using A/C inside our houses / apartments. I understand that the transmission loss is lower when sending A/C, so it makes sense, but then nearly every device in my house has their own AC to DC converter. Just have one AC-DC converter per building. I'd like the future to just be USB-C sockets in my house. We have USB-C PD 3.1 which supports up to 48v, I imagine…

At USB voltages, one or two volts of drop is significant. You need very heavy cables, and for every voltage USB-PD allows you'd need another set of cables.

Also, some devices run directly on AC, or need more than USB can do, even with EPR. Since we already need AC for that, why add more wires when USB chargers are cheap and efficient and reliable these days?

Re: Building my own solar power system

#347
post #328

Earlier quoted context omitted.

You're mischaracterising "not wanting to overpay" and "getting something you need in return for what you have in excess" as "greed". It's a pointless conversation if you're willing to do that. You're just changing definitions before arguing them.

I will allow for sake of argument then trading for needs to be excepted. Under your definition it would also implode, just not fully destruct.

Trading for wants is no different to trading for needs from a capitalism perspective. It just removes the need for a central bureaucracy that decides what counts as a need.

Re: Building my own solar power system

#348

Earlier quoted context omitted.

I’m in a mountain town in BC Canada and pay $0.13/kWh. My 7.8kW solar system cost me $0 out of pocket after incentives and an interest free loan. It’s making ~$1000 per year of electricity, so we’ll just put that onto the loan for the next 8 years instead of paying it to the power company. Then for ~25 years after that it will make me $1000/year. Free money. (The price of electricity is already pre-approved to increa…

Why pay off an interest free loan?

It has to be paid off in 10 years.

Re: Building my own solar power system

#349
post #306

Earlier quoted context omitted.

Unfortunately I can no longer edit the post, but of course you’re right. Max generated power is proportional to (blade length)^2, therefore quadratic, not exponential.

I assumed that meant that big windmills would be much cheaper per watt than small ones, but according to what I'm finding in https://news.ycombinator.com/item?id=44056971 , that doesn't seem to be the case. Small rooftop windmills may actually be cheaper !

There’s another limiting factor though, which is that power is also proportional to (wind speed)^3, and the wind is greater higher up.

Although having said that, I do believe the main reasons we don’t use them in the UK are noise and wildlife concerns. In many ways the total efficiency doesn’t matter if it’s generating enough power.

Re: Building my own solar power system

#350

Earlier quoted context omitted.

That’s silly, why make it political? If anything the political encroachment came from the green crowd first, cafe standards, EV mandates and the like. The best way forward has always been to explore all energy avenues, and that will include fossil fuels as well. At least you’ve included nuclear, but left out fission, strangely, which is the best hope of electric generation replacement we currently have. I’m tired of…

No offence, but everything is political. Much of our lives are controlled by laws. These laws are all politically controlled. To say it's silly to make something political, usually suggests your supported political slant is difficult to justify. Trade offs are only possible when the party in charge is willing to work with EVERYONE, we don't have that now. Thus the criticism.

Politics works through division by way of laws. Reduce the laws, reduce the division, and therefore politics.
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