Good morning all. And welcome back to the ChargeSync blog, which has been lying low for a little while as we addressed some technical challenges. Good news though (providing you like these blogs and/or technical progress) we’re back to bang the embedded batteries drum.
This week the plan is to address the issue of battery placement. High voltage grid, low voltage grid? Where should you put your new technology, and why?
To understand the problem of battery placement we need to understand what constraints the power system faces and how it deals with them.
Part 1: Energy
The first challenge is how to provide sufficient energy at any one instant in time to meet the needs of users on the system. Batteries can be added to either previously uncontrollable demand or previously uncontrollable generation to ‘flatten’ or manage the profile to reduce costs. Crucially a flatter demand (or uncontrollable generation) profile is cheaper and easier to serve or support on the network.
Why is a profile flattened by batteries cheaper for the grid to produce?
Flexible generation is currently used to provide shape or profile on the system. Thermal (gas and coal) generation to meet the demand shape, and to do so we will need to either switch lots of small plant on and off (starting plant is usually expensive) or run larger plant at ‘part load’. Unfortunately running an engine at part load means running the engine at a lower efficiency. And lower efficiencies (or more start costs) means a more expensive cost of provision for your energy, and a higher bill.
Now if the demand profile is flatter because batteries have moved the demand (or generation in the case of renewables) from one period which was over supplied to another which was under supplied, and provided that this is done with a cost in battery system efficiency terms which is lower than the cost of part loading or starting new plant to solve the problem, then batteries are reducing the cost of providing your energy.
Part 2: Flows
Moving on from energy, the next, and more interesting challenge from a battery perspective is that of flow constraints. The wires on the network could be considered to be a series of connected “pipes” along which energy (electricity) can flow. Just like pipes the wires have a limit to their capacity. Physically if you flow too much power through the wires then they heat up and become damaged, even eventually melting.
Why is this important?
Because the way the power grid currently operates is to size the network to meet peak demand (maximum possible I), and rightly so because you don’t want to melt the wires every day after Eastenders. This is expensive as you need a wire which is big enough to flow currents which might only occur once in a blue moon, the rest of the time your pipe is too big. And the effect is worse than you think because it’s not linear, it’s I*I (£4.7bn according to this article). Because of this charges are levied on the system to make it more expensive for peak time energy users (all of us) to use power. In the old days we couldn’t control the timing of our consumption of power without creating inconvenience in our lives (moving your tea from 18:00 to 20:00 for example). But the concept of controllable demand, in our case being controllable storage means that we can generate a much flatter demand profile by moving consumption from peak times to non-peak times which means because we’re reducing peak demand and peak flows, it’s less expensive for the grid to service. Crucially, to reduce the flows through the wires where these losses occur batteries need to be placed close to the demand., so that flows through the wires are increased during off peak periods (and the pipe is far from full, but decreased through the most congested periods.
In summary then:
- Looking at energy alone a logical use for batteries is to smooth demand, or uncontrollable renewable generation to reduce the cost of supply meeting demand on the grid
- Provided storage efficiencies are of order efficiency losses for part loading thermal plant storage should provide competitive energy shaping capability
- Energy alone doesn’t tell us where batteries would be best located on a network.
- Where you put your batteries on the grid is important. We believe the logical place is at the point of demand. Placing batteries at the point of demand helps to solve the energy problem, and the flow constraints issue. Placing batteries next to unpredictable generation only solves the energy part of the issue.
- To ensure a market incentivises batteries in the right places battery operators need to have access to the value they create (or costs they save) on the grid. Market change is required to achieve this.
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