Electricity demand response is being adopted in many countries to help electricity companies cope with the fluctuations in supply which are inherent in most renewable energy technologies except for anaerobic digestion. Anaerobic digestion with its high up-time and 24/7 power production capability, is not a part of this problem. In fact, anaerobic digestion, with its ability to store biogas as an energy source, can help by the production of electricity which can be switched on and off, to order.
Now that demand response is also considered as mainstream methodology to bring about the strategy of decarbonisation and sustainable development we thought that we would write this article, to discuss how AD Plant facilities may become involved in the electricity demand response market.
Demand response (called load response by some) is defined as:
“The ability for qualifying end-use commercial customers to reduce their use of electricity when wholesale prices are high or the reliability of the electric grid is threatened. In turn, customers who participate receive discounted rates.”
On the demand side, and also the electricity companies are increasingly using “demand response” techniques, on the supply side, by allowing potential power contributors to be made into the grid by allowing bidding for instant response peak demand period supply contracts. These are either directly overseen by National-Grid, or awarded and administrated through 3rd parties.
According to the September 2016 edition of Water & Wastewater Treatment, in the UK the following Demand-Side opportunities are available to the right businesses, amounting in all to some 15 schemes:
1. Short Term Operating Reserve (STOR):
An important source of reserve energy for National Grid, STOR is procured through 3 tenders throughout each year. Users contract to reduce usage by a specified amount with a response time of 20 minutes.
2. Demand Side Balancing Reserve (DSBR):
A time-limited tendered product aimed at major energy users willing to reduce their electricity use between 4pm and 8pm on winter weekdays in return for payment.
3. Fast Reserve:
A monthly tendered market designed to procure large blocks of reserve energy of 50MW to respond within 2 minutes.
4. Firm Frequency Response (FFR):
A monthly electronically tendered service through which National Grid procures energy that can respond within 30 seconds.
5. Demand turn-up:
A new service, under development, which will pay businesses to increase demand when there's too much energy in the system, typically responding within 10 minutes.
6. Triad Avoidance:
The practice of reducing consumption at periods where peak winter national demand is forecast (Triads), in order to reduce the transmission charges that are levied on major users.
For AD Plant power generators, the opportunities which seem most likely to suit the AD Plant operator will be 3., and 4.
Few AD Plants will be large enough to participate in the Fast Reserve 2 minute requirement, unless their owners were to install dedicated engine-sets fuelled by dedicated biogas storage. However, as long as the site has the capacity to inject an additional 50MW the high price paid for the energy produced may make such an investment profitable.
To service the Firm Frequency Response (FFR) requirement for a 30 second response time, AD plant operators could possibly install battery banks, with the batteries re-charged using biogas generated electricity.
The information systems to automatically communicate to the remote electricity demand response equipment will be essential to move the electricity supply industry from the existing grid systems, to the new “smart” power grid.
The smart power grid will be essential to improve the ability of the grid operators to balance electricity supply and demand. It will be designed to do it by transferring electrical power loading to split second accuracy as an electricity demand response, initiated at each electricity demand response event. Each power injection event will need to be instigated based on an pre-assessed calculated supply gap, and paid for at the appropriate high electricity prices.
All this requires a new type of an information system, namely a computer based Demand Response system.