Is the ‘point’ of solar about to change? | Hacker News Reader

Is the ‘point’ of solar about to change?

iijiij.com

11 pointsaniijbod16 comments

This is an incredibly lazy blog article. The author hasn't even attempted to do any calculations he's just contemplating someone else doing them.

I don't think he has thought the problem through or researched it at all. Reading the wiki article ( http://en.wikipedia.org/wiki/Photovoltaic_power_station#Sola... ) shows that people already make the calculations of whether to pay for sun tracking which gets you an extra 30% energy. Obviously at some point the tracking mechanism will cost more than 30% of the energy produced. That's the cut off. And at that point the arrays installed will be fixed non tracking arrays tilted towards the equator at an angle calculated to get the maximum energy during the year.

"get the maximum energy during the year."

There are already countries where the cost of electricity from PV is below the cost of electricity bought from the grid. In these countries every Watt you generate yourself saves you money.

These users don't want to get the maximum amount of energy per year, they want to minimize the amount of electricity bought from the grid. They want to better match the generation profile of solar to their load profile. i.e. spread generation across the day - instead of getting it in one big peak in the middle of the day. To do this - it is already common to install east and west facing PV.

But I agree lazy journalism - he's speculating about a future which has already happened in some places.

Solar farms already do this. Optimal angle always tracking the sun.

I have panels on my roof in England - today they generated 22.5kWh. That's roughly 3 times my daily need https://mobile.twitter.com/Edent_Solar/status/45541993526384...

The issue isn't generation as much as it is storage. My south facing roof should generate my yearly kWh - but I have no practical way of sorting that energy. A multi kWh battery like in a Tesla if just far to expensive to stock in my attic.

Very naïve question:

What are the issues with moving a liquid (water?) from a low storage tank (in say your basement) to a high storage tank (say in your attic) and then at night let it flow in the opposite direction to produce electricity? I haven't done the calculations, but would it require too much liquid or maintenance?

I'm also not sure what this would be called? Gravity Battery?

I'm also too lazy to actually do the calculation, but to a Fermi approximation XKCD has already more or less proven[1] that it's not terribly practical for a homeowner as an energy storage solution.

[1] https://what-if.xkcd.com/91/

converting to and from mechanical energy is inefficient. But it has been done in some places.

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

I mean, I figured it was worse than a battery, but if you can store it much more cheaply it might have been worth it? EDIT: The link also goes through some of the pros and cons. Thanks!

And cool, my guess at a name wasn't too far off:)

Well, back of a fag packet calculation...

Let's lift 1KG of water up 5 meters.

That will require 50 joules of energy (5 * 9.81).

Suppose I want to store 5kWh of energy (half my usage).

1kWh = 3600000J

5kWh = 18000000J

1KG of water is 1 litre.

I need to store 360,000 litres of water - that's a bit too much did domestic use :-)

Is large here - but I think that's about right.

It's called pumped storage. It exists, but only at larger scales than a household system. It's ~80 efficient.

http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity

No way to feed to the grid? Or is that to hard at the moment?

I feed it into the grid so others can use - but that's not exactly self sufficient storage.

Even if the solar modules are free, there is still a cost of equipment, land/roof, labor, soft-costs, etc.. And if the cost premium of tracking is outweighed by the the value of the increased production, then tracking will continue.

In short, there is no one-size-fits-all answer whether tracking is cost-effective now or with dramatically different module prices.

Sure, the panel is getting cheaper. But transportation, installation, and land are not. It is still likely that panels will be more cost effective than more complicated, expensive installations, but probably either oriented to the sun at noon, and make sure there are as many as possible in that orientation in the space available. And anyway, it would just be half a pyramid. no point in orienting them to the north in the northern hemisphere or to the south in the southern hemisphere.

Can someone point to a source of what "cheap" solar material/panel they are talking about?

They are talking about the decreasing cost of solar cells over time.

http://blogs.scientificamerican.com/guest-blog/2011/03/16/sm...

Buckminster Fuller style domes sound like a good bet.

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