Solar Power

Is there any chance of being electrocuted by solar panels?
Is there a risk for firefighters when they enter a building where there is solar power and stand in a puddle of water if there is short between the solar panels and the water.
They cut normal power before entering buildings, but do you get enough juice from residential solar panels to consider this as a risk?
edit: you could place a normal off switch on the solar array and hook it up to the fire alarm for industrial systems, the switch should open even when power fails.
And you are correct in saying that it is the current that kills, but you still have to have enough volts to get a decent current trough a human (no mater what the max current output is).
The real question is then do solar panels have a fixed current output (then its dangerous) or a fixed voltage (then with max 50 volts is even wet not a problem)

solar panels are usually 12 or 24 volts for the smaller ones, and those voltages are pretty safe.

larger arrays can be connected in series or parallel, depending on the battery configuration. It’s likely for a large installation to produce 48 volts or even higher, and those voltages can be dangerous.

Higher voltages are used on large installations to cut down on the cost of the wiring.

But, any solar array has an inverter somewhere, running off a battery, and that will output 120 or 240 VAC, and that is definitely dangerous.

So this raises an interesting point. Should all solar panel installations include a cutoff switch accessible to fire fighters? It looks like they should. The switch has to cutoff the voltage from the array, and also turn off the inverter.

edit: but switching off the voltage from the array is not enough, as the array is still putting out power (assuming the sun is shining). One possibility is to use a multiple pole relay located very near the array to open both + and – leads from the array. Thus there is no path for the current to get to ground. If water got everything wet, the array would short across itself but still be isolated from ground. But what if the relay fails?

Max, you seem to have the idea that it takes a lot of current to be dangerous. No, 20mA can shock you, 50mA can kill you, and there are a lot of arrays that can put out 48 volts at many amps.

edit2:
"edit: you could place a normal off switch on the solar array and hook it up to the fire alarm for industrial systems, the switch should open even when power fails. And you are correct in saying that it is the current that kills, but you still have to have enough volts to get a decent current trough a human (no mater what the max current output is). The real question is then do solar panels have a fixed current output (then its dangerous) or a fixed voltage (then with max 50 volts is even wet not a problem)"

sorry, 50 volts IS a problem, lots of people have been killed from 50 volts. I admit it is not as likely as with 100 or 200 volts, but it is still possible, specially with a lot of water around. I don’t remember the UL spec offhand, but I think it is somewhere around 20 volts.

solar panels have a variable voltage, dependent on the amount of light on them. You have to plan on the highest possible voltage. The current output is usually in the tens of amps or higher, more than enough to kill, so it is the voltage that will determine the current through your body.

edit3: dividing up the world into constant voltage sources and constant current sources is meaningless, as neither exists in real life. All voltage sources are a imperfect voltage source or an imperfect current source or something in between.
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I hope to create a solar/ steam residential power station. My idea involved fresnel lenses to focus heat on water as well as molten salt for possible overnight use. The salt and water boilers, so to speak, can be made with refractive propertied ceramics, or so I am informed. Any technical advice or a line on generators , steam engine sources would be great.

Reinventing the wheel is never a good idea. A lot of research has gone into solar energy systems. Look what´s on the market right now, and ask yourself why nobody has improved on it.

Steam engines and generators are not efficient, about 30%, nor easy to run or install. You will need a superheated steam boiler, a turbine and a very complicated installation. They require a lot of operation and maintenance.

If you want to store heat for overnight use, the best thing is solar with a very large storage tank.
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This would be for a residential area and need to comply to fire and other safety regulations. I want to generate electric power for home and electric vehicles.

You’re asking a difficult question only because the technology is improving each month. What is the best today probably won’t be the best next year. For wind power you will need a wind availibility survey describing the average wind conditions throughout the year for your locality. Every homesite is a bit different. To establish a cost/benefit analysis your first have to know how much wind energy is available.

My engineering class is looking for wind and solar kits for residential system in Washington state. Our budget is $12,000. We need a whole kit. And it should generate at least 1000 watts.

A typical home needs about a 2000 or 3000 Watt (2 or 3 kW) solar power unit. To power your toaster , it will take 1000 Watts. To power your hair dryer, it takes maybe 1500 to 1800 Watts. A Microwave might be from 800 to 1500 Watts. If you opt for a 1000 Watt system, you may have to walk around with wet hair, and cold sandwiches.
The prices for a complete 2 or 3 kW unit runs about $20,000 to $30,000 installed. Or about $10 per Watt (or about $10,000 per 1000 Watt or 1 kW). With the utility company rebates/ buydowns/ incentives, you may get the cost down to $8 to $9/ Watt. So, you may be able to do install a 1000 Watt system for $12,000, but not sure — it could be close.

The main reasons being:
1) The solar unit will work well for 6 or 8 hours a day — but when the sun goes down, your power is zero. So to make it effective, you have to have battery banks. It would require several batteries at about $100 each to store the power during the day, so you will have power at night. Absolutely needed for a stand-alone system if you need power at night. These batteries have an expected lifetime of maybe 5 years or less. They will need replaced in 5 years.

2) The solar unit will provide 12 Volt DC power. Your house uses 120 Volts to run your microwave and toaster and TV. Therefore — you will need an expensive electronic piece called an inverter. It converts 12 Volt DC power to 120 Volt AC power. This adds to your budget, and it is expensive. And it is electronic — it will fail at some point. Sometimes it lasts 5 , 6, or 8 years — then needs replaced — at considerable cost.

Your thoughts on "wind power" are even more gloomy. Similar issues as with solar. It works when the wind blows at least 7 mph. If the wind is not strong enough, you get no power. And think about it — a warm summer day is not too hot when the wind is blowing. But the very "hot" summer days — it is "very hot" because there is no wind blowing. Hot days have little or no wind blowing or else they would be just a "warm day". Hot day means — no fan or no A/C.

The $12,000 budget could maybe install a 1 kW solar unit, but you would have to give up a hair dryer and microwave, electric oven, electric clothes dryer. Unless you are into a candle light dinner with cold sandwiches, a more realistic solution will cost about $20,000 to $30,000 for a 2 or 3 kW solar unit, with battery backup.

Hello, I’m a student conducting a short open-ended survey to get a feel of how solar-powered installations at home will be perceived and received by the average person. Your responses will help me develop a sustainable product for residential use. Feel free to respond and send me your comments. Thank you very much for helping! – MariaCGL

We used to have solar pannels on our roof that powered some lightbulbs in our house. This was in the Philippines more than 10 years ago. It seemed to work, although I think there was some sort of back up power since we had lights even during cloudy and stormy days. I suppose it would be nice to have solar powered appliances as long as it has a backup power source for those short and cloudy winter days. I think it would be great to have some sockets that are connected to a mini station that is constatntly being recharged by solar power. That way you can plug anything in the socket and recharge your moblie or use a hair dryer or reading lamp. It would also be handy for those rare days of power cuts so that even if the main power source is cut due to a storm or something, you will still be able to use those little essential appliances by plugging them into the sockets. I hope this helps!