How CHP can stabilise stressed out power networks
The cost and carbon saving potential of cogeneration has long been appreciated, but its role in providing stability to power networks is increasingly important.
CHP is a flexible and agile technology. Its rotating momentum provides a good level of inertia to stabilise the network and manage system stresses when there is too little or too much power. This is particularly useful in complementing intermittent sources, such as wind and solar. The big advantage of CHP is its speed of response to a sudden mismatch between power production and consumption.
As the UK energy industry makes the turbulent transition from fossil fuels to renewables, CHP's complementary network balancing role is crucial in keeping the lights on. The introduction of European Network Codes, especially the Requirements for Generators (RfG), is preparing CHP for an even greater role in accommodating the rapid growth of renewables.
Such modifications to equipment are enabling the distribution network to shift loads to compensate for excess renewable generation when demand for electricity is low. The features being requested of generators under the new codes will give the system operators both inbuilt, automatic, and remotely controlled tools to better control the voltage and frequency of the grid. These changes, together with other initiatives such as Demand Turn Up, give system operators a comprehensive tool kit to deal with the evolving grid of the future.
In a study by the National Bureau of Economic Research (NBER), researchers concluded that the expansion of intermittent wind and solar power still requires support from electricity generated by natural gas.
The report 'Bridging the Gap: Do Fast Reacting Fossil Technologies Facilities Renewable Energy Diffusion?' argues that, in the absence of viable storage options, renewable energy integration has been made possible by 'fast-reacting mid-merit fossil-based technologies', which act as back-up capacity.
The authors state: “Fast-reacting fossil technologies, which includes most gas-generation technologies, combined heat and power and integrated gasification combined cycle to name a few, are characterized by mid-merit order, quick ramp-up times, lower capital costs and modularity (meaning that efficiency does not fall significantly with size). They are thus particularly suitable to meet peak demand and mitigate the variability of renewables.”
Drawing on the flexibility of CHP and linking it with SMART/microgrids provides a powerful system that not only delivers cheap, reliable low carbon energy at a local level, but allows participation in wider system operational aspects. One example is 'Smart Cornwall', which will develop the U.K’s first integrated smart energy network. Research to assess the potential of virtual power networks was undertaken by ENER-G in partnership with Advanced Digital Institute; Flexitricity; Smarter Grid Solutions and UK Power Networks.
The research consortium completed extensive simulation and modelling, using real data from ENER-G CHP systems and UK Power Networks' London electricity network. This demonstrated the scale of the opportunity for tapping into the inherent flexibility of existing decentralised CHP supply network to relieve peaks in electrical demand. This is seen as a more cost-efficient way of increasing network capacity and performance.
Active Virtual Power Plants - linking highly energy efficient CHP units via a decentralised smart-grid - can provide the flexible, low carbon, cost effective answer to modern energy challenges. This can help to solve the energy trilemma of improving energy security for local consumers, reducing costs and also decarbonising supplies. Simply burying more copper in the ground and building additional large power plants to expand the existing system is unsustainable - both environmentally and from a cost point of view.
One often overlooked aspect of the growth of gas power generation and its increasingly flexible operation is the role played by the gas distribution network operators. Ensuring the gas supply network can respond to sudden peaks and troughs in demand as the flexible generators respond to the network dynamics is vital to release the full potential of CHP for electricity grid stabilisation and balancing services. The gas network operators can help stabilise the power grid by ensuring that the gas network is capable of meeting an increasingly spiky gas demand CHP brings as it responds to new commercial drivers.
Finally it shouldn't be forgotten that small scale CHP is considered one of lowest cost carbon abatement technologies available due to the large primary energy savings it can achieve. CHP can, therefore, provide the clean and reliable answer to demand side response - combining both flexibility and lower emissions to perfectly match the requirements of the capacity market. The cost benefits of CHP are particularly attractive at the current time, when wholesale gas prices are relatively low and tax saving incentives apply, including UK exemption from the Climate Change Levy for small-scale installations and access to Enhanced Capital Allowances. CHP's additional commercial potential in balancing the power network, makes it an even more attractive financial proposition.
For further information read the Essential Guide to CHP