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Comment by rodionos | Hacker News Reader

The runaway favorite in wind energy is Denmark, where wind turbines, predominantly offshore-based, produced 44% of the total energy production in 2016.

https://apps.axibase.com/slider/energinet-2016/?slide=2

However, wind energy production is remarkably volatile with the minimum and maximum average hourly production per day being two orders of magnitude apart: 912.7 MWh (min) vs 102.6 GWh (max).

https://apps.axibase.com/slider/energinet-2016/?slide=24

They started incentivizing solar generation since it is counter-seasonal compared to wind, wind is stronger in winter months.

https://apps.axibase.com/slider/energinet-2016/?slide=5

This is not sufficient however, so sufficient reserved conventional capacity and interconnects to Norway (hydro) and Germany (gas) is something that helps them even out production on abnormal days.

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Hydro + Wind + Solar is a powerfull mix. Hydro tends to have fixed power per year, and a lot of flexibility when you release that power. Solar matches the daily demand in most areas, though Denmark is very far north to produce solar they can import solar from the south.

Wind is really cheap and provides some power 24/7 but does not match the demand curve. So even then you still needs some backup power either from pumped hydro or peaking power plants.

IMO, the real downside is the electric grid becomes even more complex to manage and takes real investments to handle shifting supply.

Real investment usually means lots of real jobs. So win win.

Yeah that sounds like the perfect mix of generation technologies. Only thing missing is pumped hydro storage for some of those GWh days.

Pumped hydro requires very specific geography to make it viable, which is why it's present in so few places. That's why so many people are investigating other storage systems: batteries, compressed air, flywheels, etc.

You can shift electricity a thousand+ miles with minimal losses. Outside of small islands the real limitation is political borders. You can easily used pumped hydro on any major landmass, but ideal locations are often across a border which very closely ties your infrastructure with another country.

PS: The Rio Madeira transmission link in Brazil, with an overhead length of 2,385km, is the world's longest power transmission line. The geometry get's complex as you can effectively sift power from location A to D by offsetting the direction you send power from intermediary production at B and C.

I was under the impression that line losses were rather high, until I did a quick bit of research and found that they are at around 5 to 6% nation wide [1]. At those levels, it can easily make sense to transmit the power to a location that has better storage.

[1] https://www.eia.gov/tools/faqs/faq.cfm?id=105&t=3

The real limitation is mostly technical: dynamically matching supply and demand when some or most of your supplies' outputs are directly controllable is a hard problem in a large, complicated, distributed grid.

Compressed air is probably one of the worst possible ways to store energy, because you cannot achieve more than a low-single digit percent efficiency. Thermodynamics is not your friend when compressing and decompressing air.

http://orbit.dtu.dk/files/6324034/prod21323243995265.ecos201... claims 29-43%, which still isn't great but better than single digits.

The highest point in Denmark is ~170m high.

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