Solar ... In the news

gefnew

You then have this to keep grass down.

silverwhistle

Looks like some juicy bits in the shade there...

70sbudgie

gefnew said:

You then have this to keep grass down.

Does this actually happen? I get the theory, but aren't sheep prone to eating everything - including loose, low hanging cables?

QrizB

QrizB said:

Martyn1981 said:

This isn't a serious argument, just a fun one, but as I understand it plants/crops are about 3% efficient(?) at converting sunlight to energy (I think that's across a year), and even lower efficiency for grazing as there's a second step of conversion from (say) grass to meat. But PV is now around 20% efficient. So ..... and now I'm getting 'well dodgy' with the comparison, but how does importing food compare economically to importing energy, or even UK FF's?

I ran the numbers on growing oilseed for biodiesel vs. PV last year, I think. I can't find the thread now but from memory, PV won out handsomely. Rather than putting 7% biodiesel in road fuel, we'd make bigger carbon reductions by planting the same acreage of PV panels.

Turns out I was mis-remembering, and my calculation was on page 299 of this thread:

QrizB said:

I didn't catch Farming Today but, as a back-of-an-envelope calculation:

• A hectare is 1/100th of a square kilometre, 10,000 square metres.
• A hectare of maize will yield around 17 tonnes of dry biomass* or roughly 85MWh if burned as fuel.
• A hectare of solar panel will hold around 1MWp of solar panel** which will generate 1000MWh/yr of electricity.

And maize needs sunny fields (see map at "yield" link) so solar farms seem to be a clear win.

* Links for yield and energy.

** Assuming 20% efficient panels at 50% effective coverage, and 1kWh/Wp.

That's the maths for biodigestion or direct combustion. How about biodiesel?

There's a useful Wikipedia table here:

https://en.wikipedia.org/wiki/Table_of_biodiesel_crop_yields

According to that table, a hectare of rapeseed will yield 1190 litres of oil. At about 10kWh per litre, that's 12MWh of oil per year (you'd expect this to be much less than the maize yield above, since only a small part of the rapeseed crop is oil).

What would this mean for carbon emissions?

• Burning a litre of diesel creates 2600g of CO2 so 1190 litres from a hectare of rapeseed oil averts 3.1 tonnes of CO2.
• The carbon intensity of the UK grid varies, but is typically around 180g/kWh (from Drax). 1000MWh from a hectare of solar PV averts 180 tonnes of CO2, 60x as much as a hectare of rapeseed.
  

How sensitive is this calculation? For eaxample, can we grow a different crop, and are we over-estimating the carbon intensity of the grid?

• From the Wikipedia list, even oil palm only yields 6000 litres of oil per year (5x as much as rapeseed) and we're not likely to see successful oil palm plantations in the UK any time soon. That would avert 15.6 tonnes of CO2.
  
• At the start of the year, the carbon intensity of the grid was about 80g/kWh. If that was achieved year-round, our 1000MWh of solar electricity would only avert 80 tonnes of CO2.

Looking at relatively extreme cases, solar PV is still about 5x more effective at reducing CO2 emissions than biodiesel is.

Martyn1981

70sbudgie said:

gefnew said:

You then have this to keep grass down.

Does this actually happen? I get the theory, but aren't sheep prone to eating everything - including loose, low hanging cables?

Yep, lots of sheep grazing and PV. Beef is much trickier, the panels have to be higher, and far more rugged as they'll scratch/rub themselves on it. And apparently goats are a no no, they'll eat anything they can get, and can jump/climb extremely well.

Pigs and chickens are fine, but a different approach often using PV on sheds (may be very, very large sheds).


Back to the sheep, and CW's comment, we've got an E/W garden, and the lawn to the south, against a 1.5m high fence, in the shade, is the part that grows best, even during this summer's low rain / drought. Too much sun will reduce grass growth, especially if rain is low. Plus (and I think it was Eric who pointed this out many years ago), there are many types of grass, and the shade loving type will find its way over time.

Lastly, can be nice for the animals too, with lots of pics of sheep and cattle lying in the shade/shadow from PV or a wind turbine tower, on hot sunny days.



Funny looking sheep/PV!

Martyn1981

Pushback against the possible changes to land use for PV. But to be fair, just like I have a 'vested interest' being pro-RE, I suppose it's fair to say that landowners too have a vested interest. But I think their arguments are reasonable.

And I still think a crucial factor is one raised by Michaels, pointing out that the amount of land (3b or otherwise) that is used for PV, and will ever be used for PV, is almost miniscule.

Landowners call for scrapping of plans to ban solar energy from England’s farmland

Farmers have urged whoever succeeds Liz Truss as UK prime minister to abandon plans to ban solar energy from most of England’s farmland, arguing that it would hurt food security by cutting off a vital income stream.

Truss, who resigned on Thursday, and her environment secretary, Ranil Jayawardena, hoped to ban solar from about 41% of the land area of England, or about 58% of agricultural land, the Guardian revealed last week.

They planned to do this by reclassifying less productive farmland as “best and most valuable”, making it more difficult to use for energy infrastructure.

Members of the Country Land and Business Association (CLA), which represents 33,000 landowners, told the Guardian having solar on their less productive land allowed them to subsidise food production during less successful years, as well as providing cheap power for their estates and homes in their local area.

Teacher does not understand all the fuss, adding: “As a proposition they are quite easily hidden by a large hedge. They don’t make noise, there are no moving parts. Carbon is a serious thing we all have to consider now, solar panels have to be part of that. If the argument is that the land is lost for food – you may be aware that the planning applications for solar parks are done on a temporary basis – ours is a 25-year period. If, for whatever reason, we run out of food, which is extraordinarily unlikely, we can pull it all up and restore it to agriculture.

“We make unequivocally more from our solar panels than from farming. There is a gut reaction people have to any sort of greenfield development and it is more of a reaction to people’s response to seeing solar parks – I don’t think it’s a real fear for food production.”

Coastalwatch

A glimmer of hope for a brighter future perhaps, although how long before the inquiry reaches a conclusion is unclear. Let's hope the Prime Ministers decision to now attend COP27 is an indication of a fresh approach from Government.

As Mart has so often observed the economics of renewable energy are unquestionable, so just maybe, those now in charge and realising the dire financial state we are in will prioritise the most economic and sustainable solutions. 

Solar Energy UK welcomes Commons inquiry into solar technologies and storage

“The Prime Minister’s decision to attend COP27 and emphasising the economic, energy security and carbon benefits of renewables is to be welcomed,” said Hewett.

“It also appears to signal that the new government has abandoned former Environment Secretary Ranil Jayawardena’s plans to sabotage the expansion of cheap power from solar farms, which would have been a disastrous policy. To settle investor concerns, however, we still need greater clarity from the top of government.”

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

Exiled_Tyke

Coastalwatch said:

A glimmer of hope for a brighter future perhaps, although how long before the inquiry reaches a conclusion is unclear. Let's hope the Prime Ministers decision to now attend COP27 is an indication of a fresh approach from Government.

As Mart has so often observed the economics of renewable energy are unquestionable, so just maybe, those now in charge and realising the dire financial state we are in will prioritise the most economic and sustainable solutions. 

Solar Energy UK welcomes Commons inquiry into solar technologies and storage

“The Prime Minister’s decision to attend COP27 and emphasising the economic, energy security and carbon benefits of renewables is to be welcomed,” said Hewett.

“It also appears to signal that the new government has abandoned former Environment Secretary Ranil Jayawardena’s plans to sabotage the expansion of cheap power from solar farms, which would have been a disastrous policy. To settle investor concerns, however, we still need greater clarity from the top of government.”

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

Together with this news:

https://www.bbc.co.uk/news/business-63507630

that the next Sizewell construction is also under review and we might just possibly be heading in the right direction.

A question has just occurred to me. In building a nuclear power station, is the environmental affect of pouring so much concrete a) significant and b) ever debated in the green credentials of nuclear?

Martyn1981

Hiya ET. Short answer, yes.

The build of new nuclear is actually quite low carbon given the small footprint and long running times. So it comes out highly competitive with wind and PV on construction.

But (come on, you knew there was going to be a but) ....... the work involved in decommissioning, and the massive work needed for long term storage depositories, pushes nuclear CO2 emissions higher. But still not the end of the World.

BUT .... the emissions from FF generation for an extra 10-15yrs (v's rolling out far faster RE*), when divided across 40-60 yrs for nuclear, make it far higher than RE, plus of course for the same money you can get 2-3x as much RE generation, and for the same subsidy support, perhaps 10-20x as much RE generation.

So new nuclear builds starting in the 80/90's would have been great, but now, it doesn't work as CO2 displacement nor economically v's alternatives.

Cost wise, it looks like tidal lagoons could match or beat new nuclear, and provide a similar amount of annual leccy as HPC + SZC. As Z has pointed out so many times, tidal solutions would also help with intermittency, broadening the RE toolbox.


*Just in case it looks like I'm cheating, as offshore wind for example takes over a decade from the start of research, and provisional permissions, it's crucial to remember that's there's a huge pipeline for RE at all times. These projects may be in development for many years before applications for actual construction / CfD contracts are made.

For reference, look at the CfD round 4 results issued this year (July). We have PV being contracted for commissioning in 2023/24 & 2024/25, onshore wind for 2024/25, and offshore wind in 2026/27 (see page 8). [Btw, just the offshore wind contracted in round 4 alone, should generate more leccy pa than HPC (or SZC).]

Even if SZC got permission and contracts issued today, I doubt it could be generating before 2035.

Edit - Sorry, should have said commissioned before 2035. Likely that one (of the two reactors) would start generating 2yrs earlier.

Exiled_Tyke

Wow ! Brilliant, informative and thorough response Martyn.  Thank you .  (But in reality would I ever expect anything less from you?)