an extrapolation about solar energy

http://phys.org/news/2015-03-large-scale-deployment-solar-photovoltaics.html
"...Use of solar photovoltaics has been growing at a phenomenal rate: Worldwide installed capacity has seen sustained growth averaging 43 percent per year since 2000..."


http://www.c2es.org/technology/factsheet/solar
"Solar power also accounted for 0.5 percent of global electricity demand in 2011..."

From these two statistical facts above of the current rate of 43% per year increase in electric generation from solar (assuming that "Worldwide installed capacity" is approximately proportional to electric generation from solar ) and 0.5% of world electricity being generated from solar from 2011, If my maths is right, I extrapolate that, hypothetically, if that 43% per year increase is maintained for the next 11 years, we would be generating 100% of our electricity from solar at some time within the year 2026.

Obviously, that extrapolation is making at least two big assumptions that are probably both false;
1, our demand for electric energy will not increase.
2, the current rate of increase of electricity generation from solar will be maintained.

+ the smaller assumption (I think ) that worldwide installed capacity of solar photovoltaics is approximately proportional to electric generation from solar.

Obviously, it is also unrealistic that we would abandon other forms of electric generation esp renewable one's.

Originally posted by humy
http://phys.org/news/2015-03-large-scale-deployment-solar-photovoltaics.html
"...Use of solar photovoltaics has been growing at a phenomenal rate: Worldwide installed capacity has seen sustained growth averaging 43 percent per year since 2000..."


http://www.c2es.org/technology/factsheet/solar
"Solar power also accounted for 0.5 percent of global electric ...[text shortened]... s also unrealistic that we would abandon other forms of electric generation esp renewable one's.

And, the US has a special problem with solar, that is, going big time with it.

The solar states are the deserts of the west, but that is exactly where the infrastructure, the high tension lines are NOT.

It has been estimated the cost for that project, totally outside the cost of installing square kilometers of solar panels, is in the trillions of dollars to get the electricity generated and stored onsite to the coastal cities where it is mostly consumed. LA, Seattle, NYC, Miami, Dallas, etc.

Originally posted by sonhouse
And, the US has a special problem with solar, that is, going big time with it.

The solar states are the deserts of the west, but that is exactly where the infrastructure, the high tension lines are NOT.

It has been estimated the cost for that project, totally outside the cost of installing square kilometers of solar panels, is in the trillions of doll ...[text shortened]... onsite to the coastal cities where it is mostly consumed. LA, Seattle, NYC, Miami, Dallas, etc.

I suggest that the way forward for the US is, at least for now, stick to putting solar panels on the roofs of houses for local electricity demand only despite that meaning putting them in the less favorable local climate.

However, personally, if I was a politician, regardless of in which country; US or UK, I would be pressing very hard for creating a super-grid for the whole of the country and even the whole of the world. Initial costs of this will be extremely high but I believe well worth it as it will pay for itself in the long run and not just because this would allow transport of solar electricity from deserts to where it is needed. It would allow the world to much more easily go all-renewable partly because it would make it easier to transport the energy very long distances to where it is most needed thus allow renewable electricity to be generated where renewables work best, and partly because it would virtually eliminate the need for expensive off-the-grid energy storage which also would otherwise waste significant amounts of energy during charge and discharge.

Originally posted by sonhouse
And, the US has a special problem with solar, that is, going big time with it.

Although you are correct, it is totally unnecessary to even talk about it, as it is a long way from actually being a problem. The reality is that not all the US's energy will come from solar for a very long time in the future. Even if it goes completely renewable, solar will likely remain under 25% of the total.
More importantly, a significant proportion of solar generation will be roof top installations and not large scale solar farms in the desert. And even for large scale installations, although the desert may be the best option efficiency wise, it is not the only place that solar is viable. Germany has managed to build solar farms without having any deserts, the US can too. In fact solar farms would probably work well almost anywhere in the US, if the price of the hardware comes down.

Originally posted by twhitehead
Although you are correct, it is totally unnecessary to even talk about it, as it is a long way from actually being a problem. The reality is that not all the US's energy will come from solar for a very long time in the future. Even if it goes completely renewable, solar will likely remain under 25% of the total.
More importantly, a significant proportion ...[text shortened]... rms would probably work well almost anywhere in the US, if the price of the hardware comes down.

There is a US company called Solarcity, they are doing just that:

http://phys.org/news/2015-03-solarcity-microgrids-tesla-batteries.html

Originally posted by humy
http://phys.org/news/2015-03-large-scale-deployment-solar-photovoltaics.html
"...Use of solar photovoltaics has been growing at a phenomenal rate: Worldwide installed capacity has seen sustained growth averaging 43 percent per year since 2000..."


http://www.c2es.org/technology/factsheet/solar
"Solar power also accounted for 0.5 percent of global electric ...[text shortened]... s also unrealistic that we would abandon other forms of electric generation esp renewable one's.

The U.K.s energy demand is of the order of 50 gigawatts. The maximum energy from solar radiation is 500 Watts per square metre (in space it's more like 150-300 W/m² at ground level). Allowing for solar cell efficiency and cloud cover etc. this comes to 50 watts per square metre (as a fairly generous estimate). So that's 1 billion square metres or 100,000 hectares of solar panels or about 1000 km². The UK's land surface (according to Wikipedia) is 243,000 km². So that's of the order of 0.5% of the available land surface turned into solar panel. With something like 30 million households that's of the order of 300 square metres per household. The average rooftop installation is more like 20 square metres. So I doubt that solar power will ever produce much more than 10% - 20% of the UK's power demand. Which is a handy addition, don't misunderstand me, but solar alone is not going to supply the UK's energy needs.

Originally posted by DeepThought
The U.K.s energy demand is of the order of 50 gigawatts.

Is that including transport?

With something like 30 million households that's of the order of 300 square metres per household. The average rooftop installation is more like 20 square metres.
That suggests that households currently constitute a less than 10% of energy demand. Is this correct?

Germany gets about 6% of its electricity from solar. Do they have more than 6% of their roofs already covered?

Originally posted by twhitehead
Is that including transport?

[b]With something like 30 million households that's of the order of 300 square metres per household. The average rooftop installation is more like 20 square metres.
That suggests that households currently constitute a less than 10% of energy demand. Is this correct?[/b]

No, electricity generation only. According to the Wikipedia page in 2014 the UK had a total capacity of 5GW of solar production. The total insolation is 110 W/m², so my estimate of 50W/m² is looking overgenerous. They're aiming for 22GW by 2020.

This relies on it being sunny, so power has to be generated on rainy days. 10% maximum capacity sounds about right.

Originally posted by DeepThought
They're aiming for 22GW by 2020.

So roughly 30% of current demand? Seems your calculations were way off.

I do see from Wikipedia that the UK gets roughly only half as much sun as Germany, so maybe solar is not the best option for the UK, especially the northern latitudes.

However, you still have wind, geothermal, biogas, tidal and more to choose from. A good energy policy includes a mix.

http://en.wikipedia.org/wiki/Solar_power_in_the_United_Kingdom

Originally posted by twhitehead
Germany gets about 6% of its electricity from solar. Do they have more than 6% of their roofs already covered?

+ why not adapt solar panels for the surfaces of roads and paths?
(that isn't even a new idea )

+ I actually did a calculation a long time back and worked out that, if you covered my rooftop of my small house, that will on average more than cover all my personal domestic electric demand.

Originally posted by humy
+ why not adapt solar panels for the surfaces of roads and paths?
(that isn't even a new idea )

It has been considered, but I am not convinced of the benefits. There is currently no shortage of space for solar panels, so if its being done for space issue, then don't. If it is being done because roads and paths cost money anyway and road with built in solar panel works out cheaper than road+solar panel separately then maybe. But there still remains the issues of who owns it, and wiring etc.

+ I actually did a calculation a long time back and worked out that, if you covered my rooftop of my small house, that will on average more than cover all my personal domestic electric demand.
Approximately what latitude?
Certainly the first step towards universal rooftop solar is a utility buy back policy as that negates the need for local storage in every home, which is currently a large part of the cost of solar.

Originally posted by twhitehead

Approximately what latitude?

I live in the middle of England. The weather here is far from ideal for solar and yet, with energy storage, I have calculated roof-top solar panels could on average meet by personal demand for electricity except for perhaps about one month in mid-winter. But the reason I am not rushing to do that is that the initial costs of such a setup would be just too high for me to manage although I assume it would probably all pay for itself in the long run.

Originally posted by DeepThought
The U.K.s energy demand is of the order of 50 gigawatts. The maximum energy from solar radiation is 500 Watts per square metre (in space it's more like 150-300 W/m² at ground level). Allowing for solar cell efficiency and cloud cover etc. this comes to 50 watts per square metre (as a fairly generous estimate). So that's 1 billion square metres or 100, ...[text shortened]... addition, don't misunderstand me, but solar alone is not going to supply the UK's energy needs.

In space the amount of solar energy is 1355 watts per square meter. Maybe 1000 watts per square meter on the ground and then 20% of that, so about 200 watts per square meter out the door.

Originally posted by humy
I have calculated roof-top solar panels could on average meet by personal demand for electricity ....

I assume that doesn't include heating? Do you use gas?