Solar ... In the news

QrizB

Swan_Valley said:

Some 369MW installed in 2021 was rooftop solar, the highest total since 2015, said Solar Energy UK.

That must be around 100k homes? Not too shabby. Now I need to look for UK housebuilding stats to see how they compare.

Martyn1981

Using solar panels to reduce the amount of sun/heat hitting crops is showing great results in Kenya.

Kenya to use solar panels to boost crops by ‘harvesting the sun twice’

Solar panels are not a new way of providing cheap power across much of the African continent, where there is rarely a shortage of sunshine. But growing crops underneath the panels is, and the process has had such promising trials in Kenya that it will be deployed this week in open-field farms.

Known as agrivoltaics, the technique harvests solar energy twice: where panels have traditionally been used to harness the sun’s rays to generate energy, they are also utilised to provide shade for growing crops, helping to retain moisture in the soil and boosting growth.

An initial year-long research collaboration between the University of Sheffield and the Kajiado-based Latia Agripreneurship Institute has shown promising results in the semi-arid Kajiado county, a 90-minute drive from the Kenyan capital of Nairobi and this week the full project will be officially launched.

For example, cabbages grown under the 180, 345-watt solar panels have been a third bigger, and healthier, than those grown in control plots with the same amount of fertiliser and water.

The solar panels do not just reduce water loss from plants and the soil – their shade mitigates some of the stress experienced by plants due to high day temperatures and UV damage, Randle-Boggis said.

Verdigris

On a related subject, I heard, on Farming Today, this morning, that if fields used for growing maize for bio-digestion were used as solar parks the energy yield is up to 23 times higher.

JKenH

Verdigris said:

On a related subject, I heard, on Farming Today, this morning, that if fields used for growing maize for bio-digestion were used as solar parks the energy yield is up to 23 times higher.

You do have to take into account that solar generation isn’t always available when you want it but at 23 times the yield you could buy a lot of storage and still come out ahead. 

Verdigris

Indeed. And there is also a win in avoiding the soil erosion and carbon release caused by growing maize. With the right sort of vegetation under the panels you could sequester carbon, provide wildlife havens and/or raise some tasty organic chickens or lamb!

QrizB

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.

Verdigris

The problem is that maize is an ideal feedstock to raise the calorific value of the other waste that goes in the digestors; council compostible waste collections, supermarket and food processor waste, catering waste, etc.

Time to breed a high energy, dwarf, short growth cycle crop, to harvest between the panels?

michaels

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.

How much synthetic fuel could be made using that 1000MWh of PV electricity - more or less than the 85MWh from burning the corn oil?

Verdigris

from burning the corn oil?

They don't burn corn oil. They put the whole plant into an anaerobic digestor, which produces methane, which drives a generator to produce electricity. The waste heat from the generator help to heat the digestor to speed up the reaction.

QrizB

michaels said:

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.

How much synthetic fuel could be made using that 1000MWh of PV electricity - more or less than the 85MWh from burning the corn oil?

85MWh is from drying and burning the entire crop, stalks and leaves and all; corn oil or bioethanol will be a small fraction of that.

Claimed energy efficiency of electrolysing water (to make hydrogen) is around 50%, so that would give 500MWh of gaseous fuel.

Converting that into ammonia or methanol at 25% efficiency (a guess on my part, Google is failing me) would give 125MWh of liquid fuel, still more than the gross energy of the maize.