Solar PV Survey Sensor Advice

Conor20

Hi all, I plan on installing a Solar PV array on the house next year, either on the south facing roof of the house, or on the roof of a shed which also faces south. To decide between the two, I'd like to mount a sensor which would record the solar energy each surface is receiving throughout the day for a few months.

I see some handheld meters available which do exactly this, but they don't seem suitable for leaving mounted on a roof for months at a time. They're also quite expensive at ~€300.
The Seaward Solar Survey 200R Irradiance Meter is an example of a handheld unit: "The Seaward Solar Survey 200R is an extremely versatile 6 in 1 Solar Site Survey Meter: Irradiance Meter, Digital Compass, Digital inclinometer, Ambient Thermometer, PV Panel Thermometer and Datalogger. It has a datalogging solar irradiance meter ideal for Solar Surveyors, installers and engineers when performing a solar site assessment or surveys."

Does anyone know of cheaper and more suitable sensors which I could mount on the two roofs for a few months, which would log data on an hourly basis to measure the exact solar energy being received?

Thanks,
Conor.

rolion

Save the hassle...

Get the most open available space that face south and cover it with panels.
Fit them portrait or landscape so that no physical obstacle are in the path
Also, don't forget the cabling from panels to battery modules/charger/inverter, there is a considerable loss if they are running in big length.
Get them as well in an appropriate place that will hold easily to access and safe all the above auxiliary modules.

Myself, i downloaded an astronomy program called Stellarium, set my GPS location and checked time-forwarding the position of Sun in relation to my house. The angle that it Summer time and the big difference with the Winter angle...
Kind of plan for position for Winter time, to maximise the coverage/exposure/the angle.

What's is budget, how many panels you'll get ?
On grid / off grid ?

Have fun...

Conor20

Thanks Rolion. I have already modeled the theoretical generation using the NREL Solar PV modeler and Helioscope, which I guess is pretty similar to Stellarium which you suggest, so I have a rough theoretical figure for these two locations. What I'm not sure about is shading. It's harder to model this without actually measuring the sunlight hitting the areas with a sensor. The shed roof is unshaded to the south, but when the sun is at lower latitudes (when it would be less strong, so probably not a big deal) it may be shaded to the east and west. The solar survey sensor would be to check how much this would be a factor.

One question with your advice of covering the best surface with PV panels: The south facing roof is on the front of the house. I understand there is a planning exemption for putting solar PV or HW solar on the front of a house up to 50% of the roof area. It would be more eccomonical to cover the entire roof, which entails planning permission. Has anyone gone down this route? It sounds like it makes more sense than just covering 50% of the roof to avail of the planning exemption.

More info on the solar tools I used:
From another thread:

Conor20 wrote: »

NREL have a useful tool here which will take the location of your house, apply the local sunshine hours, etc. and calculate the estimated output for each month. You can play around with the inverter efficiencies, etc. if you want. This is what I get for a 4kW array:


Helioscope lets you draw out the panel area, then select panel makes, inverters, etc. and will model the energy output, again for the sunshine records for your area:

quentingargan

Shading would be disproportionately high at this time of year, and the only real data you could get from a sensor would need a year of monitoring.

The planning exemption is half the roof up to a max of 12 sq m. That is only seven panels. So if you even want to go to an 8 panel system, you would still need planning.

The economics of this depend on getting paid for surplus electricity that you don't use. There is a consultation process on this ongoing with DCENR at present, but it is widely expected that there will be some sort of payment scheme late next year. At that stage, it would probably turn out to have been a good move, but there is no certainty. Unless you use a lot of electricity and can use all the power yourself.

Conor20

quentingargan wrote: »

Shading would be disproportionately high at this time of year, and the only real data you could get from a sensor would need a year of monitoring.

Makes sense. By the sounds of it, using solar sensors isn't really something people do for domestic installations. Being a data junky, I tend towards trying to fully understand things with certainty.

quentingargan wrote: »

The planning exemption is half the roof up to a max of 12 sq m. That is only seven panels. So if you even want to go to an 8 panel system, you would still need planning.

Thanks. Does anyone have experience with the planning process for Solar Panels? It is difficult and expensive? I don't mind going through red tape even if it's to add one or two panels, given they'll be improving the payback of the system for perhaps 20 years to come.

One other question related to the planning exemption: For a semi-detached house which shares it's roof with the neighbour's - does the 50% apply to "your" half of the roof? As in you can cover a maximum of 50% of the 50% of the total roof space?

quentingargan wrote: »

The economics of this depend on getting paid for surplus electricity that you don't use. There is a consultation process on this ongoing with DCENR at present, but it is widely expected that there will be some sort of payment scheme late next year. At that stage, it would probably turn out to have been a good move, but there is no certainty. Unless you use a lot of electricity and can use all the power yourself.

Yep. A feed in tariff would remove the need for a battery system, which would make things a lot more efficient and economical, so hopefully that comes through.