Jump to content

Solar Panel for Obsy?

Earl

By Earl
in DIY Astronomer

Recommended Posts

  • Replies 28
  • Created
  • Last Reply
Vega

Vega

Posted
Posted

I use a 110ah marine battery and keep it hooked up to 2 solar panels (4.5w + 1.5w) all day to trickle charge it. If the battery is healthily charged initially, this keeps it good all year. Due to the low wattage there's no need for a charge controller.

Matt

Link to comment
Share on other sites
Smeg

Smeg

Posted
Posted

Go read all the Wattage usage on all your equipment you will plug into it OR get a socket wattage METER and then it will tell you what you ACTUALLY use.

Make sure it is an accurate socket meter or a clip on inductive cable meter (onto a socket extender - I use very heavy power spike connectors as I live up a mountain with lightening and power cuts/spikes/browns lol).

When you are done using it to see what you need for your solar power, you can use it around the house to see what actually sucks up your power bill :)

Link to comment
Share on other sites
pete_l

pete_l

Posted
Posted

Let's run some ballpark numbers.

Taking as an example the 80W panel mentioned below. The dimensions of that come out at just over 0.6m² of area - but with the holes between the PV elements, let's round that down to 0.5m² of sunlight-collecting material.

Now, the monocrstalline material in those particular panels has a maximum efficiency of 18%. So for every 100Watts of sunlight that falls on the 0.5m² of collector, you'd get 18Watts of electricity out.

Next, you need to know how bright the sunlight will be on your panel and how many hours per day (or per week) you'll get that amount of sun. Weather stations in Spain (ref: here for example) record that amount of solar radiation each day. At the absolute peak of summer, they get about 30MJ/m²/day which works out as an average of 460 Watts/m² - obviously at high-noon it's errr higher, but over the day that's the average.

The panel in question is 0.5m² and 18% efficient, so a completely sunny day in southern Spain, with the panel always pointing directly at the sun would give you an average of:

460 * 0.5 * 0.18 = 41.7 Watts

For each of the 18 or so hours that the sun was shining on it. You can see that's a long, long way away from the peak quoted figure of 80Watts. :p

It gets worse. That's Spain - the sun is higher and the clouds are fewer. De-rate the sunshine by say: 25% for Britain (Spain gets UV levels of 11 or 12 :), we don't) and de-reate again for the number of hours of sunlight - on average, maybe 6 hours of sun and 12 of cloud during daytime during the summer. A realistic figure for the output of this PV panel in England would therefore be:

42Watts * 75% * 6 / 18 = 10 and a bit Watts, on average. It will get some charging during cloudy periods, so let's say 15Watts to include that.

That's the good news. Now the bad news. In the winter the sun is lower and the number of sunny days is fewer. The spanish MJ/m²/day figures go down to one third in the winter, so our 15Watts of battery charging power becomes 5Watts on a sunny winters day - just because the sun is weaker.

When you factor in

  1. The fewer sunny days in winter
  2. The longer hours of observing

then an 80Watt panel probably won't hack it.

Sorry to be the bearer of bad news ...

Link to comment
Share on other sites
Smeg

Smeg

Posted
Posted
It is a very cool idea though, an enviromentally sustainable observatory. Nice. Fits right in with the ethos of any Astronomer I reckon. Keep us updated as to your progress, I think it's a great idea if it's a goer.

Pitty the rest of the observatory is made from Oil (Plastics) and Felled tree's (probably not replanted) and machined in factories (more oil and smoke), and the batteries made from metal's from the ground along with the panels made from metals again mined from the ground.

Link to comment
Share on other sites
Earl

Earl

Posted
  • Author
Posted
You could supplement the solar panel with an exercise bike so you have a green back up, plus you keep fit.

Easy now!!!!

Did any one see the science program where they powered a bath and fridge with a bike.

Was fun

Link to comment
Share on other sites
Earl

Earl

Posted
  • Author
Posted
Let's run some ballpark numbers.

Taking as an example the 80W panel mentioned below. The dimensions of that come out at just over 0.6m² of area - but with the holes between the PV elements, let's round that down to 0.5m² of sunlight-collecting material.

Now, the monocrstalline material in those particular panels has a maximum efficiency of 18%. So for every 100Watts of sunlight that falls on the 0.5m² of collector, you'd get 18Watts of electricity out.

Next, you need to know how bright the sunlight will be on your panel and how many hours per day (or per week) you'll get that amount of sun. Weather stations in Spain (ref: here for example) record that amount of solar radiation each day. At the absolute peak of summer, they get about 30MJ/m²/day which works out as an average of 460 Watts/m² - obviously at high-noon it's errr higher, but over the day that's the average.

The panel in question is 0.5m² and 18% efficient, so a completely sunny day in southern Spain, with the panel always pointing directly at the sun would give you an average of:

460 * 0.5 * 0.18 = 41.7 Watts

For each of the 18 or so hours that the sun was shining on it. You can see that's a long, long way away from the peak quoted figure of 80Watts. :)

It gets worse. That's Spain - the sun is higher and the clouds are fewer. De-rate the sunshine by say: 25% for Britain (Spain gets UV levels of 11 or 12 :), we don't) and de-reate again for the number of hours of sunlight - on average, maybe 6 hours of sun and 12 of cloud during daytime during the summer. A realistic figure for the output of this PV panel in England would therefore be:

42Watts * 75% * 6 / 18 = 10 and a bit Watts, on average. It will get some charging during cloudy periods, so let's say 15Watts to include that.

That's the good news. Now the bad news. In the winter the sun is lower and the number of sunny days is fewer. The spanish MJ/m²/day figures go down to one third in the winter, so our 15Watts of battery charging power becomes 5Watts on a sunny winters day - just because the sun is weaker.

When you factor in

  1. The fewer sunny days in winter
  2. The longer hours of observing

then an 80Watt panel probably won't hack it.

Sorry to be the bearer of bad news ...

Not bad news at all, just good information :p

Link to comment
Share on other sites
ncjunk

ncjunk

Posted
Posted
Easy now!!!!

Did any one see the science program where they powered a bath and fridge with a bike.

Was fun

Was that the one where the people inside didnt know what was powering the house and the cyclists looked....very put out when they switched the oven on? I enjoyed that!

By the way he is quoting southern spain, us in the north in winter get a lot more cloud and rain. I would love a solar panel set up.

Link to comment
Share on other sites
CGolder

CGolder

Posted
Posted

did the factor in the actual nights you would use the observatory?

i use a 40w and a 110ah leasure battery and i havent had to charge it yet in the 3 months i have had it i have probably plugged into it half a dozen times to run the scope

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.