Power-To-Heat Systems Get Going In Germany
Originally published on Renewables International.
By Craig Morris
What to do about all that excess electricity at times of low or negative spot market prices? Use it to generate heat in a district heat network!
Increasingly, firms and communities are investing in power-to-heat or P2H systems in Germany. Last year, there were negative prices on the power exchange on 25 days, up from 15 days in 2012 and only 6 in 2011 (report in German).
A recent project at Südzucker, a foodstuffs (sugar) producer, is a good example (report in German). It needs to offer 10 MW of uptake capacity and be able to ramp by 2 MW per minute. It is connected to the medium-voltage grid. The entire storage tank only takes up, however, 60 square meters. “A lot more sites are available for P2H than previously thought,” one expert from Enerstorage, Südzucker’s contracting partner, is quoted.
It should be noted that the signals for power storage as heat are not negative wholesale market prices, but ancillary services. In other words, power is taken from the grid when the frequency rises.
The P2H process is highly efficient and inexpensive – nearly 100 percent according to a report on a similar facility in Augsburg (in German). Connected last fall, it also has an uptake of 10 MW.
Wikipedia provides of list of the some two dozen P2H facilities in Germany along with more in the pipeline (in German). It also points out that Denmark is a leader in the technology, having opened numerous such systems in the 2000s. The Danes, of course, needed P2H sooner; they already have roughly 40% wind power alone, compared to around 20% wind and solar combined last year in Germany.
Reprinted with permission.
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Is this power to heat via a heat exchanger, or power to heat via a resistor?
or is it a heat pump? sounds like resistance heating, which is not very efficient actually. but, if there are only 25 instances per year, and I assume they’re only a few hours per instance, then not a bad way to go, but the overall benefit isn’t much either. If this happened every day, then a heat pump technology that moves 300% of the heat relative to the electricity input would be much more efficient.
If electricity prices keep going negative, it’d be more “efficient” to use resistive heat! 🙂
Since this must have very fast ramp rates, produces process steam, and is episodic, the system is undoubtedly resistive. ( I have just looked up the company Enerstorage and they use ‘Elektrodenheizkessel’, i.e. boilers with resistive heating).
This is a very important idea – home heating is a big problem for the future. Eventually, we will have enough RE infrastructure to routinely produce a large excess of energy, and home heating would be a truly excellent value-added service for at least half of the population.
Is this not how places like universities, large businesses, office complexes, etc provide heating? A central boiler sends out steam or hot water via insulated pipes to all satellite locations?
Neighborhoods, communities, cities could do the same with their collectively-owned RE farms. It would be a lot less expensive than retrofitting many hundreds of millions of heat pumps into many tens of millions of American homes.
I think the idea of thermal storage, as a means of grid balancing and demand shift. Is just taking baby steps, it will look totally different in 10-20 years.
I have to disagree with you somewhat on this. Very few American homes get their heat via hot water or steam sent from another building, and installing such a system would be more expensive than individual heat pumps for each home. In places where heat is distributed in pipes, like the college I went to, yes, using electric resistance to consume excess renewable electricity would be smart and economical.
I read somewhere (can’t remember where, it was weeks ago) that Germany has a problem with excess electricity in winter because many coal-burning generators also supply piped heat to surrounding buildings, and so must run to heat the neighbors even while wind contributes plenty of power.
This could only work in apartment buildings in cities, or small towns with a central energy station. and a pre-existent water system. IF homes already have central heating, all one has to do is supply two pipes into the house. Most northern homes require multiple heat exchangers, and the power to run them. That’s tens of thousands of dollars for equipment alone. Two pipes – peanuts.
If we plan our energy future right, it will be a very different landscape than now – energy will be superabundant and cheap, planning and expenses can be shared as commons projects with economy-of-scale and lack of redundancy to keep costs low. Basically, the complete opposite of what we see right now – with every homeowner looking out for himself only, and every install duplicating the expensive components. (A million homes, a million inverters, etc)