[HN Gopher] The Basics of Photovoltaic Systems: How They Work
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The Basics of Photovoltaic Systems: How They Work
Author : cleantech
Score : 50 points
Date : 2023-10-11 02:24 UTC (13 hours ago)
(HTM) web link (mercurialtrends.com)
(TXT) w3m dump (mercurialtrends.com)
| bruce511 wrote:
| As someone who has acquired rather too much information about
| solar over the past few years (in preparation for a largish
| system) I can say this is a good overall primary.
|
| One irrelevant detail not mentioned, which I like repeating, is
| that despite being made to literally sun-bathe all day long,
| solar panels don't like being hot. (Effeciency drops with heat,
| gains with cold.)
|
| There's not a whole lot you can do about this, except allow for
| passive air cooling. There are some water cooled panels
| available, but costs make them uneconomic for now.
|
| I was interested to learn though that on a cold summers day, the
| panel output can exceed the nominal rating got the panel.
| Something to consider if you are at high altitude.
| stinos wrote:
| _solar panels don 't like being hot_
|
| Indeed, and this touches on the 'Regular cleaning of PV panels
| is important for ensuring maximum energy production' statement
| in a funny way. First of all, while the statement is accurate,
| I'd say is not too important practically depending on where you
| live. As our isntallation guys also told us. Our panels seem to
| do just fine with occasional heavy rainfall to clean them and
| the loss when they're covered in a thin layer of dust is not
| worth spending time on. On the other hand, the PV cleaning
| companies will say that it's super important to clean them. So
| when my mum got her panels cleaned it went like this: sunny
| day, panels get hot, efficiency drops. Panels were cleaned with
| water, temperature drops, cleaners told her 'look how much
| better it is now'. But after they were gone temperature rose
| again and efficiency was essentially back to where it was
| before.
| boredemployee wrote:
| >> solar panels don't like being hot
|
| that's why in tropical countries people should aim for
| photothermical systems instead, collecting sun energy with
| parabolical mirrors heating up water, moving steam engine thus
| generating energy
| RetroTechie wrote:
| > solar panels don't like being hot.
|
| For boats there's flexible panels that in many cases you can
| even walk on.
|
| But the sun's power not turned into electricity, heats both
| panel & roof of the boat (and in turn, its interior). Not
| something you want on a hot sunny day.
|
| A rack-mounted panel otoh, allows for airflow underneath, and
| -if roof mounted- separates (potentially hot) panel from the
| boat's roof.
|
| So, cool(er) vs. aesthetics. Definitely a pitfall to be aware
| of for boat owners installing PV.
| tibbydudeza wrote:
| Had to get a home PV system out of necessity due to our
| national power company being up a shitcreek with an aging fleet
| of badly maintained coal power plants.
|
| 3.7 Kw solar panels and 2 x 5KW LifePO batteries and a 5Kw
| SunSynk inverter tied to the grid - solar geyser and it does
| not power our electric oven - the only issue is the management
| system is dumb as bricks - there is no intelligence and
| difference charge settings or profiles for our cold winters and
| hot summers or using the weather forecast for the day.
|
| It just averages out.
| adql wrote:
| If it can be controlled via RS485 you might be able to add
| some smarts to it, like lowering charge level if weather is
| supposed to be good next few days.
| victor106 wrote:
| Off-topic: The most practical alternative energy seems to
| nuclear
| hutzlibu wrote:
| "There are some water cooled panels available, but costs make
| them uneconomic for now."
|
| Couldn't you just use that warm water and so make it economic?
| Are there any combined systems that try this?
| adql wrote:
| There are but you just won't be able to use all that water if
| you have more than a few panels.
|
| Like if you need enough water for shower you might just need
| heat of like... one or two solar panel sized heaters,
| anything extra means water will be permanently hot and so any
| benefits from cooling would be minimal unless you had some
| heat dump to pump the excess heat out. So more cost
|
| There is probably some use for heating house in the
| spring/autumn, but system that can put the heat from panels
| either to heat the water or heat the house is additional
| extra complexity and cost.
| edent wrote:
| You can, but the problem is that warm water isn't that
| useful.
|
| Unless your system can regularly heat up to >60C to kill
| legionella then it will need external heating.
|
| Secondly, when the external temperatures are high there's
| very little need for warm water. Perhaps a few dozen litres
| for washing. No one is taking a hot bath on a summer's day!
|
| If you have the space, you can store the hot water
| underground and then pump it back up in winter for heating.
| But that's expensive.
| robertlagrant wrote:
| I'm not sure where you could use it. At least in the UK:
|
| - water for heating your home is in a closed loop, and you
| wouldn't want to add this cooling to that closed loop as it
| would heat up your solar panels on cold days
|
| - water for drinking/washing comes from the same cold feed,
| and you don't want to heat that up as you can't get cold
| water then
|
| - bisecting the water supply into hot taps and cold taps, and
| running the hot one under the PV cells could work, but it
| would only flow the water when something is pulling water,
| e.g. running a tap, which might be a hindrance to cooling
| Maakuth wrote:
| There are solutions in the market for this. The heat
| recovery system is filled with glycol solution, which means
| it doesn't freeze over even if left unpowered during sub-
| zero outside temperature. Then there's a temperature sensor
| and a control unit that only runs the pump when the fluid
| in the panels is warmer than the warm water accumulator of
| the home heating system.
|
| The heat collectors are vacuum insulated, so provided with
| enough solar radiation, they will work even when it's very
| cold outside. These systems work okay for example here in
| Finland. Of course it's a limiting factor that you normally
| need the heating most when the solar radiation is at the
| minimum. If you've got a swimming pool or some other use
| for the hot water during the summer, it's a good deal.
| robertlagrant wrote:
| > the warm water accumulator of the home heating system
|
| I'm not sure how this would work in a modern UK heating
| system - there is no warm water accumulator to my
| knowledge.
| Maakuth wrote:
| I suppose a modern gas or oil burner doesn't need one.
| But this sort of solar based heater as well as ground-
| source heat pumps typically would need it. They are not
| very expensive however, as they are just heat-insulated
| tanks of water. Of course space requirements and such
| might rule out adding one in many cases.
| robertlagrant wrote:
| I think it's more - how do you hook it up with the rest
| of your water?
| Angostura wrote:
| There are lots of houses in the UK that have hot water
| tanks. The water in these is heated by effectively a
| radiator inside the water tank. We have one here and the my
| tank has a 'secondary loop' designed to be driven by a
| water-filled solar panel. Typical kind of tank:
| https://www.screwfix.com/p/heatrae-sadia-megaflo-eco-
| solar-p...
| robertlagrant wrote:
| True, but those are often older. I know some new builds
| also have them (I lived in one of said new builds a few
| years ago) but my impression is they are often older
| heating systems that don't have a combi boiler yet.
| senectus1 wrote:
| its not the running of them thats uneconomical, is the added
| infrastructure and component cost.
| darkwater wrote:
| Yep, I live in Southern Europe and my panels have the biggest
| output end of April/May, while one would expect it to be end of
| June.
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(page generated 2023-10-11 16:01 UTC)