August 2009 |
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Distributed Energy Resources and Storage
With the big smart grid standards roadmap conference coming up in Washington
on the third and fourth, I am going to stick with writing about what this
means for buildings. |
Toby Considine |
Storage is the keystone technology for the smart grid, and for alternative energy. Good energy storage does more than anything else to reduce the strain on the grid. Good energy storage reduces the pay-back time and improves the reliability of on-site alternative energy more than anything else. On-site storage in the end nodes of the grid, in the commercial building, in industry, or in the home, is the clearest path to reliability. Only storage reduces the dependence on central resources.
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A smart grid embraces distributed energy resources (DER),
whether for generation or for storage. Cost effective DER works best with
distributed ownership and operation. Distributed ownership allows each site to
choose how much reliability and how little dependence on the grid it wants.
Distributed ownership and operation allows for a diversity of technologies, as
individual owners make their own decisions on what works best for them. The end
node may have its DER, including storage in an individual building, or on a
campus / microgrid. Such resources are not likely to be under the direct control
of the distribution or transmission operator.
And yet, there is a temptation to write the standards for communicating with and
about storage as if they were under the direct control of the utility. Just as
some visions of the smart grid include direct control of building automation
systems by the utility, some see it necessary for the utility to perform direct
control of all energy storage as well. Either approach is wrong because it
limits innovation. Either is wrong because it moves an area of entrepreneurial
innovation into a regulated business. It’s not all about electricity. It’s not
all about the grid.
Energy storage is much more than batteries, and does not wait on new battery
technology. Thermal storage, particularly storing cold in summer, is already
taking off as a smart grid technology; the old fashioned water heater does the
same. Energy can be stored as water pumped up into storage tanks. The ranch I
grew up on used wind instead of electricity to place water 40 feet in the air,
where our water pressure was stored. Pump storage is not just for mountain
lakes.
A Scandinavian project painted streets in alternating regions of white and
black. They used the black to gather heat for a piping system under the street,
pumped down by convection into a heat well underground for optimized heating in
winter. Same project dissipated winter heat under the white pavement to create a
second underground thermal pool - to help cool the next summer.
Almost any energy storage, whether based on thermal, chemical, or potential
energy, can be configured to provide the demand responsiveness that the grid
needs today. For most purposes, storage response is indistinguishable from any
demand response. To the grid, the response from one ice storage unit in a
basement is indistinguishable from that of dozens of technologies aggregated
across a corporate campus. Smart grid signals for storage must not lock in on
any technology or precise mode of operation. What the smart grid needs is
vibrant markets and rapid innovation in distributed storage.
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The real benefits of energy storage will not come from demand response, even if
demand response pays to develop the storage market. The real benefits of storage
will be to alternative energies.
It rarely makes sense to sell site-based generation back to the grid. Except for
industrial cogeneration, two way energy flows from the end node are a way to use
a ten thousand dollar investment distribution upgrade to buy fifty dollars of
power every other month. The true costs of measuring power and of ensuring that
your generation does not hurt my house is never summed. Transaction costs
consume most of the profit.
The value of site-based generation is to charge up site based storage. It is
reasonable to expect storage losses similar to those of preparing energy for
re-sale. In particular, site-based generation of DC electricity can be used to
charge site-based DC batteries without conversion loss. Once we have storage in
any number of houses or buildings, we have increased the value of, and shortened
the payback time for site based alternative energy.
Collaborative energy re-thinks the processes by which we manage the entire
energy life cycle. The giant broken robot that is the power grid will not be
fixed by bolting renewable technologies onto its head-end. Collaborative energy
will use economic signals to engage industry, commercial buildings, and homes.
It’s not all about electricity. It’s not all about the grid. Local energy
storage and conversion will play a big part in our future.
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