Monday, December 23, 2019

Water agencies and "virtual batteries"

Just a quick note here - I attended the Association of California Water Agencies' fall conference a few weeks back and the topic of "virtual batteries" in the water industry came up.

Water agencies use a lot of power in California - from simply pumping treated water uphill to storage tanks so water pressure still works when the power's out, to the treatment of that water and the wastewater, and to the massive distances and elevations the raw water often has to be moved to get to the treatment plants. At the same time we face an energy problem of variability in renewable energy production, with a lot of doomsaying involved over the difficulty of storing renewable power for when it's needed.

"Virtual batteries" for water agencies mean moving the times when the power is needed to when the renewable power is available, and that option is readily available for a lot of water agencies' work. The water district where I'm on the board, like most agencies, pumps water to uphill storage tanks late at night, when the electric grid has the least demand and charges the least. There's no reason why we can't pump during the day when solar power is up, or whenever wind is peaking, and the same is true for other water industry functions.

Some activities can even shift the seasons they operate, such as pumping water from large reservoirs to large aquifers for storage (or vice versa). As long as the reservoir has sufficient capacity, this could be done during the sunniest and windiest seasons of year.

I'm guessing these "unique" aspects of the water industry may not be so unique, and that a lot of other industries, and even households, can shift their time of use much more than we previously suspected.


Old_salt said...

Shifting power is not exactly being a battery, but it is a useful concept. This is especially true if there is significant supply of water so that the container only has to be filled periodically. There are lots of ways to use energy efficiently once people think about the problem and they can save money.

jrkrideau said...

Have you seen 100% Renewable Electricity ?

Canman said...

Rud Istvan wrote an energy and climate book, Blowing Smoke, back in 2014. In it, he says California passed up a great hydro storage plan to focus on delusional battery technologies. He offers lots of technical details on each.

Unknown said...

When I was at high school in the mid 60s we did a trip to a pumped storage system in N Wales at Tanygrisiau which was a hydro scheme linked to the Trawsfynydd nuclear power station. The project was started in the 50s and is still operating I believe. It was a fun trip, the nuclear power station was being serviced so we got to see more of it than normal.

Beakers said...

N fertiliser manufacture is a good candidate. Ammonia is easy to store and the demand is seasonal. As well as soaking up generation at times of low demand, the ammonia can also power generation to cover gaps in generation satisfying demand.

Brian said...

I've wondered why catalysis of water into hydrogen isn't the silver bullet of matching power production to need. I'm guessing a combo of inefficiency and cost.

Canman said...

Water not being converted to hydrogen for storage because of "a combo of inefficiency and cost", is a good guess. Rud Istvan also has a post at Climate etc. from five years ago, detailing the various methods of grid storage:

His section on challenges of hydrogen is pretty formidable:


Hydrogen can certainly be hydrolyzed from water. And the necessary electricity can certainly come from intermittent renewables. The most efficient way to convert hydrogen back to electricity at grid scale would be a PEM fuel cell or an SOFC. The math can be done using Ballard’s 1MW PEM, since a few have actually been sold as demos. Ignore the technical difficulties of bulk hydrogen storage, which the following methane alternative ‘solves’.

The theoretical efficiency of hydrolysis is ~88%. About 4% of commercial hydrogen is made this way today, with real efficiencies of ~75%. EERE says PEM fuel cells can be 60% efficient. But that is also theoretical. Ballard’s real 1 MW ClearGen® is 40±2% efficient, with a lifetime of ~15 years (similar to NaS). The round trip efficiency of a hydrogen electricity storage system would be about (0.75 * 0.4) 30%. For a utility, that is awful.

The electricity to be stored comes mainly from otherwise flexed base load generation, with chemical storage buffering renewable intermittency no different than PHS buffers peaks. The energy cost alone would be about ($57/MWh baseload / 0.3 efficiency) $190/MWh. Ballard’s ClearGen® costs about $10 million/MW (including inverter, transformer, and installation).That calculates a capital LCOE of about $114/MWh. Adding hydrolysis and H2 storage, the system LCOE is >>$304/MWh. It is simply not commercially viable–by nearly an order of magnitude. Before solving the hydrogen storage problem.

If anyone can show how this, or anything else in his post, has been superseded, ... Please do!