Solar panels - east facing

0lordy

Question: is there any point in installing solar panels for Domestic Hot Water on an east-facing roof?

While obviously it would not be as effective as south or south-west facing, I would assume there would be still be significant water heating up to the afternoon?

Mellor

0lordy wrote:

Question: is there any point in installing solar panels for Domestic Hot Water on an east-facing roof?

While obviously it would not be as effective as south or south-west facing, I would assume there would be still be significant water heating up to the afternoon?

What time of the day do you want the hot water???
South is most effective. South-west is no better than south-east in terms of amount of water heated, but one might be better than the other in terms of when the water is required, do you want hot water in the afternoon or early in the day???

0lordy

Note that I'll be installing them on an east facing roof - therefore I would get hot water in the early morning, but not so much in the afternoon/evening.

The issue is whether there any point in doing this, as I would be missing out on a lot of solar energy after midday.

0lordy

0lordy wrote:

Note that I'll be installing them on an east facing roof - therefore I would get hot water in the early morning, but not so much in the afternoon/evening.

The issue is whether there any point in doing this, as I would be missing out on a lot of solar energy after midday.

At this time of the year it's often sunnier in the mornings than in the afternoons, this is because as the sun heats up the ground it is very damp and the moisture evaporates into clouds! If you have a well insulated tank you can store the water for the rest of the day, you just need more/larger panels to harvest the same amount of energy as a south facing unit.

2 stroke

I will be facing mine east. As an experiment to see how much strength there is in the morning sun. I connected the 13 watt pv panel I am going to run my pump with to a completly flat 12 volt battery. after 5 days facing east the battery was at 12.6 volt and capable of starting a fiesta several times. Not all days were sunny but the best sunshine was in the mornings on the test days.

sesswhat

2 stroke wrote:

I will be facing mine east. As an experiment to see how much strength there is in the morning sun. I connected the 12 watt pv panel I am going to run my pump with to a completly flat 12 volt battery. after 5 days facing east the battery was at 12.6 volt and capable of starting a fiesta several times. Not all days were sunny but the best sunshine was in the mornings on the test days.

I believe the Fiesta (F for short) is the standard unit of measurement for PV panel output, which replaced the old imperial Anglia which they still use in the States.

I don't know what the figures are but I've spent a lot of time on a roof over the past few weeks and while the east-facing ones are never uncomfortable to work on in the mornings, a south-facing slate roof can be too hot to touch in the early afternoon.

Also, I can't imagine you would get much heat on an East facing roof in the Winter months, whereas you will get some to the south.

Someone must be doing some research on this for similar latitudes to Ireland.

2 stroke

I'm probably the only person on here with a solar powered fiesta. Regarding my unit of measurment it is a less vague measure than answers recieved from a certain irish PV panel suplier who couldnt define what strength of sunshine was needed to achieve the rated output. The PV panel I used is the 13 watt solar briefcase from maplin. The best output I measured from it facing due south perpendicular to strong sunshine was .8 amp @ 12.3 volt. Facing due east the best output was .72amp @ 12.2 volt. readings were taken using 2 multi meters without making correction for losses in the instruments.

I'm making my own flat plate collectors and will be happy with what heat I get for reasonable cost. Its crazy, but my esb bill is higher in summer than in the winter. The extra cost is the immersion going on in morning. Yet the sun is beaming down free energy.
When my house was built the planners refused permission to allow it face south. My east facing roof is not overlooked so I can experiment without upsetting the neighbours. When I perfect my units I will consider putting some west facing aswell. I am also considering a dummy window in south facing gable end.

Mellor

Why dont you put them on the south side no as you don't need planning for this anymore.

mad m

Mellor wrote:

Why dont you put them on the south side no as you don't need planning for this anymore.

Well up to 12meters sq I think you don't need any. I was recently omitted a front Velux rooflight, but the solar panel on front wasn't...:rolleyes:

eoghan.geraghty

Olordy if you post the exact degree they will be facing I can tell you how effective they will be and in turn how much you need to upsize your plates.
I attended some training days run by renewable energy skills network, they were independent of any specific manufacturers.
By exact degree due south is 180, east is 90 etc.

Mellor

eoghan.geraghty wrote:

Olordy if you post the exact degree they will be facing I can tell you how effective they will be and in turn how much you need to upsize your plates.
I attended some training days run by renewable energy skills network, they were independent of any specific manufacturers.
By exact degree due south is 180, east is 90 etc.

won't the effectiveness vary depending on the inclination too.

eoghan.geraghty

Mellor wrote:

won't the effectiveness vary depending on the inclination too.

quite right mellor it will, excuse me it was late and after a particularly good concert.
Thank god for handouts thats all i can say.:o

eoghan.geraghty

If your solar are plates are facing due east 90 deg,for a roof elevated 30 to 45 deg from the horizontal, you are looking at 80% efficiency.
You must oversize your system by 25% for it to be fully effective.
Roof elevation doesnt impact that much (2-3%) between 15 and 60 deg, most roofs lie in that range.

This info is from Leon Buhl, Danish Technological Institute, Industry & Energy.

If I ever get my scanner fixed, I will scan and post relevant diagrams.

Thank god for handouts;)

2 stroke

80% sounds good to me, I presume we're looking at the same efficiency on a west facing roof. For those without a south facing roof I feel the best thing to do is face half of system east and half of system west. The few hours extra sun should compensate for loss of efficiency.

eoghan.geraghty

West is marginally better, i'll try to get scanner sorted by next week or else i'm buying a new one.
And I hate buying new equipment unnecessarily:mad:

2 stroke

Had my first solar assisted shower this morning, had to turn on immersion for a few minutes, but only one panel connected yet. Had a feel good feeling all day, don't know if it was some of the goodness of the sun or the fact that I'm saving money and the planet
I need to sort out my control system. (pump running too long)
Any one know of a pipe stat designed to work on microbore pipe? (I intend to try radionics myself)
I recon there may be something going for west facing panels. Store heat over night and have earlier shower.
Ignore most of info on web from lower latitudes, they don't have sunrise as early as us or sunset as late.

2 stroke

2 stroke wrote:

Ignore most of info on web from lower latitudes, they don't have sunrise as early as us or sunset as late.

Realistically you are only ever going to get 11-12 hours max out of a flat panel, unless you either have it tracking the sun or split so that half is facing SW & the other SE

Fony Soprano

I'm probably too late replying but if you don't have a south facing roof (anywhere between SE and SW) then you need to put them on both east and west facing rooves. This will work just as well however, you should put the same number of panels of both east and west rooves, which may mean added expense (as you cannot put up just 3 panels, you must put up 4 - 2E + 2W.

coopster

you guys should check this out - http://www.emeraldenergy.ie/info/solardata.htm
from there open dublinsolardata.xls, v informative.
doin my thesis on solar efficiency just now n it doesnt look good: oil, gas etc. better up prices a fair bit before solar can stand a chance