Green Building Forum - solar energy calculator

solar energy calculator

minisaurus — Sun, 06 Mar 2022 18:13:18 +0000

Anyone know of a good online calculator? Or a method I could use to estimate what energy we might be able to generate? We're getting quotes, but I suspect the sellers' optimism might be exaggerated :)

Our house is 11 degrees 58 minutes north; our roof is a typical pointed affair, approx 30 degrees angle, approx 80 m2 roof space. One house gable points due north, the other due south, meaning we get full sun on the east facing roof in the morning, and sun on the west facing roof later in the day. We get no sun after approx 3 pm winter, 6 pm summer due to nearby trees.

We apparently get 1700 - 1800 hours of sunshine per year.

Apparently we should be able to fit approx 40 no. 400 W panels on our roof.

solar energy calculator

tychwarel — Sun, 06 Mar 2022 18:35:35 +0000

11 degrees 58 minutes North, so smack in the middle of the tropics. seems a strange place to have summer and winter.

solar energy calculator

revor — Sun, 06 Mar 2022 18:36:47 +0000

You might find useful info here.
https://www.leonics.com/support/article2_12j/articles2_12j_en.php

And

https://joint-research-centre.ec.europa.eu/pvgis-photovoltaic-geographical-information-system_en

It is not a 5 minute job working it all out.

16 Kw is a lot of output what can happen if not careful is you won't be able to use it all you can add battery which will help but depending on your DNO, you will be restricted to 3680 w export so you could apply to send more which will cost. Come winter time you will be see the benefit of a big array. If you got 3 phase at your property you can send 16Amps per phase.

solar energy calculator

Ed Davies — Sun, 06 Mar 2022 18:45:36 +0000

Posted By: minisaurus: â€œOur house is 11 degrees 58 minutes northâ€¦â€

Intriguing, where are you? That's about the latitude of Nicaragua, Gambia, southern India, Viet Nam. It's not just the latitude you need, the longitude is also important. I.e., the particular position to take into account the effect of clouds, etc.

The most commonly used tool is PVGIS: https://re.jrc.ec.europa.eu/pvg_tools/en/

On another forum about a dozen or so people reported their actual production each month for nearly a year. I collected (and published) the results in a spreadsheet. In general PVGIS was pretty accurate though a bit pessimistic: roughly a quarter of the actual readings were below the predictions from PVGIS and Â¾ were above. PVGIS has since been revised to be a bit more optimistic so I'd expect it now to be giving pretty good results.

solar energy calculator

philedge — Sun, 06 Mar 2022 19:00:04 +0000

8 kwp on each pitch would give you a nice spread of generation over the day. With a bit of shading on the west face it might be worth considering optimisers or micro inverters.

16 kwp isnt going to be cheap, more so if youre adding optimisers and or batteries.

Youll need permission from your DNO if connecting more than 3680kw. One thing to be aware of is DNOs consider total connected generation as the most youll export even though your 16kw is split 50/50 180degrees apart and will never generate anything like 16kw. If you want 16kw and the grid cant take it, youll likely need an export limitation device or pay for grid upgrade!!

PVGIS should give you a fair generation estimate but I m not sure if it will handle a split array?? It should do but Im not sure.

solar energy calculator

Peter_in_Hungary — Sun, 06 Mar 2022 19:07:14 +0000

Posted By: philedgePVGIS should give you a fair generation estimate but I m not sure if it will handle a split array?? It should do but Im not sure.

Just get an estimate for each array separately then add the results

solar energy calculator

minisaurus — Sun, 06 Mar 2022 19:08:08 +0000

Oops - er - 58 degrees 42 minutes is the latitude ...

Thank you all for the links. According to PVGIS, I'd only have to pay four months of the year ... (I have/will uploaded their file and our usage)

solar energy calculator

minisaurus — Sun, 06 Mar 2022 19:08:23 +0000

Our usage:

solar energy calculator

philedge — Sun, 06 Mar 2022 19:19:39 +0000

Posted By: minisaurus According to PVGIS, I'd only have to pay four months of the year

Unfortunately unless you only use exactly whats being generated youre unlikely to avoid grid draw for more than a short period, unless youve got storage. Without storage, as soon as the sun goes in youll be drawing on the grid having exported loads the day before, if it was sunny!

solar energy calculator

djh — Sun, 06 Mar 2022 20:29:21 +0000

400 W panels. Who knew they were a thing? I expect they're expensive.

solar energy calculator

Peter_in_Hungary — Sun, 06 Mar 2022 21:11:13 +0000

Posted By: philedgeUnfortunately unless you only use exactly whats being generated youre unlikely to avoid grid draw for more than a short period, unless youve got storage. Without storage, as soon as the sun goes in youll be drawing on the grid having exported loads the day before, if it was sunny!

Depends upon the contract with the supplier as to how you view for what you are paying.
Over here we are on annual reconciliation which means your export and import is reconciled annually so over production in the summer can balance shortfall in the winter to get net zero. However at the end of this year the system changes to monthly reconciliation for new entrants - IMO not such a good deal !! (for the consumer, probably better for the supplier).

djh.
400w panels are there (sorry about the language)
Fotovoltaikus napelem JUST 450W/24V IP68
https://www.lampak.hu/fotovoltaikus-napelem-just-450w-24v-ip68/?gclid=EAIaIQobChMI9PHkiLGy9gIV0wSiAx1-JgBLEAQYASABEgKnqvD_BwE
But when I have looked at high wattage panels before they get the higher output by being physically bigger i.e watts / m2 output is much the same.

solar energy calculator

philedge — Sun, 06 Mar 2022 23:00:27 +0000

Posted By: djh400 W panels. Who knew they were a thing? I expect they're expensive

Â£150 for 450 watts Longis... ebay 185318399888. Biggest Ive seen advertised were 600 watt

solar energy calculator

WillInAberdeen — Mon, 07 Mar 2022 09:16:07 +0000

From a few years ago:

"While in the past, sites were using mostly 60-cell p-type multi panels (ratings 240-260W), the industry is now moving to 72-cell p-type mono PERC panels with bifacial capability. This allows for 370-400W panels, with trackers and bifacial generation. This is a massive driver in compensating for the lack of subsidies today."

https://www.solarpowerportal.co.uk/news/uk_large_scale_solar_pipeline_tops_5gw_as_project_developers_return_to_acti

Leading to:
"the pipeline of large-scale solar farms shot up from a few gigawatts at the time subsidies ended a few years ago to a staggering 37GW at the start of 2022"

https://www.solarpowerportal.co.uk/news/meteoric_growth_in_new_solar_farm_planning_in_uk_sees_pipeline_reach_a_stag

I was dimly aware that something incredible and unreported was happening in UK offshore wind, but seems like utility-scale solar farms are doing the same!

solar energy calculator

fostertom — Mon, 07 Mar 2022 10:10:38 +0000

Hm - personally, my latent countryside-NIMBYism isn't activated by onshore wind farms, whose elegance I enjoy seeing en masse on trips down to A30 into Cornwall. But the solar farms along the same route are all ugly and obviously sterilise large swathes of ground, which turbines don't. So this news doesn't make me happy.

solar energy calculator

WillInAberdeen — Mon, 07 Mar 2022 10:20:42 +0000

No, that's generally not the case - appearances are deceptive! A modern agricultural field is almost a sterile environment, nothing grows/lives there except the crop - hence disastrous crash in UK insects and birds. A solar farm with rough grass below panels, is far more biodiverse, and even more so if the developer is made to plant some hedges or wildflowers.

Don't get me started on polytunnels, though!

solar energy calculator

owlman — Mon, 07 Mar 2022 10:34:44 +0000

" Don't get me started on polytunnels, though! "

Especially when they fall into disrepair and shards of microplastic are scattered to the wind.- or - they are next door to a village where the planners/architects etc will demand Conservation grade rooflights.

Now there's an idea:- You could put a few faux mullions on the solar panels and call them Conservation Grade,

solar energy calculator

fostertom — Mon, 07 Mar 2022 11:07:51 +0000

Good point Will - I hadn't connected those dots, will look at em in a new way.

Still ugly tho. Geometric purity can contrast with and nicely set off land-forms, but I hate the way these rows are carelessly smeared and tilted up and down the contours to a ragged edge, without thought to visual effect. If each panel was strictly level, a crystaline array, then the varying height-steps would chart and express the ground's shape. Rooftop arrays are usually OK in this respect.

And doesn't maintenance etc require that it's kept mown or even weed-killed as shortish grass, so other 'rough' growth, bracken, brambles, sallow etc, don't get a chance? Are the fragile structures compatible with dartmoor ponies or other stewardship-agreed animals?

solar energy calculator

Peter_in_Hungary — Mon, 07 Mar 2022 15:27:37 +0000

Posted By: WillInAberdeenA solar farm with rough grass below panels, is far more biodiverse,

Not much (to nothing) below the panels because of the rain shadow provided by the said panels. Between the rows will need maintenance, mowing to a reasonably short height would be OK but most agricultural mowers can throw up the occasional stone if too low or not shielded properly so there may be a tendency to spray herbicide to avoid this problem, but hopefully this practice could be banned.

Posted By: fostertomAre the fragile structures compatible with dartmoor ponies or other stewardship-agreed animals?

grazing around the panels would be an option if the panels were high enough to be above the height of the animals but even then damage may occur so probably the risk would be too high. (And of course nothing much of value will be under the panels because of the rain shadow).

solar energy calculator

WillInAberdeen — Mon, 07 Mar 2022 16:12:18 +0000

Peter, where would you say the rain that falls onto the panels, would end up? :-)

See eg https://scitechdaily.com/ten-ways-to-ensure-pollinators-benefit-from-the-solar-power-boom/

Developers in the UK have to demonstrate "Biodiversity Net Gain (BNG)' eg
https://cieem.net/wp-content/uploads/2020/08/BNG-case-study-28.pdf

"Figure 28.1 shows results from a single solar farm included in this study, which had been re-sown with a
wild flower meadow, whereby the number of:
Â„Â„ plant species was significantly higher in the solar farm than the control (an arable field)
Â„Â„ bumblebee species was similar between solar farm and control but the abundance on the solar farm
was significantly higher
Â„Â„ species of breeding birds was marginally higher in the solar farm and abundance was greater."

solar energy calculator

fostertom — Mon, 07 Mar 2022 17:20:38 +0000

Very interesting. Well, I would say that growth must be much less beneath the panels, even if the pathways beteen get their runoff as extra. Maybe it's more about less sunlight/photosynthesis in their shade. In hotter climates, a bit of shade may actually help, or at least widen the range of plants that could thrive.

Looks like solar farms could potentially be biodiversity +ve, but not automatically and not given present practice esp while that's allowed to include herbicide.

solar energy calculator

Peter_in_Hungary — Mon, 07 Mar 2022 17:48:05 +0000

Posted By: WillInAberdeenPeter, where would you say the rain that falls onto the panels, would end up? :-)

Dumped on the ground at the down side edge of the panel from where it would be either soaked into the ground or go as run off either way it will be of little benefit to anything growing in the middle of the panel shadow.

solar energy calculator

owlman — Mon, 07 Mar 2022 17:51:52 +0000

You could also require new farms to be on tracked arrays therefore positioning them higher of the ground and reducing overall footprint for a given capacity. The moving shadow plus height would also help biodiversity.

solar energy calculator

fostertom — Mon, 07 Mar 2022 18:11:13 +0000

How economic is tracking? Big maintenance, with 100s/1000s of mechanisms?

Imagine the dazzle, coming over the hill on a summer evening, fried by acres of glass reflecting the low sun behind me. Reagan's Star Wars!

solar energy calculator

owlman — Mon, 07 Mar 2022 20:56:50 +0000

" How economic is tracking? Big maintenance, with 100s/1000s of mechanisms "

An interesting cost-benefit analysis exercise, maybe it has been done already, I dunno.

solar energy calculator

WillInAberdeen — Mon, 07 Mar 2022 21:49:03 +0000

Lots of the issues there which are usually trotted out by the anti-renewables lobby, often they have a fear of the unknown? But if you drive off the A30 and go and look at one up close, you'll be better informed than them

- stuff grows under them, as you can see below
- they don't spray herbicide in the UK (maybe in Hungary?), so that's an improvement on the previous agricultural field which will usually have been sprayed/fertilised/ploughed to suppress native plants in favour of crop plants
- their planning consent is conditional on them not dazzling people on roads or in houses etc, easy to calculate angles during design. And on having a credible biodiversity gain plan, which becomes part of the consent.

Here's some pics to whet your appetite:

solar energy calculator

fostertom — Mon, 07 Mar 2022 21:52:48 +0000

Also, tracking, which makes sense with an isolated PV panel, so it presents its full area to sun at all times, maybe is pointless with multi-row arrays, which are spaced to 'see' all the sun that there is. Tracking won't increase that, as they'll shade each other as they come more vertical.

solar energy calculator

djh — Tue, 08 Mar 2022 10:35:19 +0000

Posted By: WillInAberdeenthey don't spray herbicide in the UK

I'd have thought that too, but there are lots of firms advertising precisely that service?

solar energy calculator

fostertom — Tue, 08 Mar 2022 10:51:26 +0000

I will find where I can view a field of tracking assemblies - can imagine they'd comply with my spec: "If each panel was strictly level, a crystaline array, then the varying height-steps would chart and express the ground's shape"

solar energy calculator

owlman — Tue, 08 Mar 2022 13:27:14 +0000

Posted By: fostertomAlso, t.............
Tracking won't increase that, as they'll shade each other as they come more vertical.

That shouldn't present a problem if the designers have done their calcs correctly. They would of course need to be more widely spaced with more natural pasture between which may aid biodiversity.
They MAY also fulfil a bit of aesthetics too, rather than the serried rows of ground mounts. Almost a bit of installation art even.

solar energy calculator

fostertom — Tue, 08 Mar 2022 13:36:24 +0000

Posted By: owlmanAlmost a bit of installation art even.

You got it