The impact of DER on the grid
In part 1, we covered how DER could be any form of decentralised generation or storage asset – from wind, to solar, to batteries and heat pumps. But these are causing a lot of problems for grid operators, all around the world. Firstly, having to accommodate increasing bidirectional flow of electricity on a network that was designed for electricity to flow from A to B. Secondly, keeping the network stable as fluctuations in supply and demand occur due to the intermittency of renewables, and thirdly the change in the electricity demand profile.
Figure 1 below shows an example of the demand profile in Western Australia (WA). There, the demand profile is changing dramatically - reducing in the middle of the day, but still peaking in the evening due to the rapid influx of solar PV on people’s rooftops. This is resulting in a reduction in demand for grid supplied electricity in the middle of the day, as people are able to self-consume their own energy. This is affectionately referred to as “the duck curve” due to the demand profile resembling the Anatidae, which I personally think is quackers!!
Figure 1 - Changes in the demand profile in the Wholesale Electricity Market (WEM) over time
Last week, on Sunday the 5th of September at 12.25hrs, WA experienced a new record system low of 986MW. The phenomenally sunny weather contributed to high PV generation (likely around 1.2GW) and it being Father's Day; with families enjoying being outside or at the beach, resulting in low consumption behaviour.
Electricity networks are built to deal with the peak. The holy grail from a network perspective would be to flatten this demand profile. If utilisation of the grid could be “less peaky” then less money would be required to augment the network, and could be put towards innovation, reducing network operational costs, and providing the end consumers with a more sustainable and affordable service.
Electrical energy storage potentially has a big role to play at plugging the intermittency challenge that renewables bring. When the sun stops shining, or the wind stops blowing, storage can be used to plug the gap. They could also be used to flatten the demand profile, and make the utilisation “less peaky”. The UK has >1GW of operational battery storage and potentially 40GW of storage in the pipeline as suggested in the Future Energy Scenarios (National Grid ESO 2021 publication).
But batteries are still expensive. Pay back times vary depending on system size, and usage requirements. For residential customers payback periods can vary from 8-16 years! The return on investment for the majority of individuals doesn’t make commercial sense, however community batteries could be the way forward. Customers can virtually store energy without the upfront capex of purchasing their own system. These shared assets not only help deal with increased DER, but they also provide network benefits such as reducing augmentation costs, stability of the grid, and maintaining power quality. The commerciality of the community batteries allows the network provider to pay the upfront costs of the asset, whilst the customer pays a subscription type fee to use the battery as service – to store excess solar PV and get paid for doing so, or to draw electricity from during peak more expensive periods.
Western Power and Synergy (the electricity retailer) are piloting 12 community batteries (called Power Banks) in an Australian-first trial to see how this potentially cost-effective solution could benefit customers and the grid. Figure 2 below highlights the demand profile on the transmission network before and after the introduction of a community battery.
Figure 2 - Battery charge and discharge profile impacting the Tx load over time
Source: Western Power
The community battery is able to charge between 10am - 2pm and increase the demand on the network. Similarly, it is able to discharge at peak times between 5pm - 8pm and as thus, reduce the demand on the network. This hasn’t completely flattened the demand profile and the “peaky” behaviour, but it has shown that a battery can go a long way towards reducing some of those big fluctuations.
Some of the key findings of the trial so far are:
⮚ Batteries can deliver network benefits (voltage support, mitigate transformer overload, address system security issues) and allow Dx and Tx operators to avoid additional capital expenditure and potentially provide a more cost-effective solution. Allowing for smaller investments that could be both modular and flexible.
⮚ Storage will need to be a key part of the solution to deal with increasing DER, but not the standalone solution, until the price point of storage technologies comes down considerably,
⮚ The market (providing essential system services) needs to develop and encourage private sector investment.
⮚Customers have a strong appetite for this type of product, however their understanding varies therefore communication and education is vital for a successful implementation.
