What’s in store for maximising the use of renewable energy?
Energy-storage technology is starting to transform the way buildings operate and opens up the possibility of a 100% renewable electricity system, says Tim Rook of BESA.
Some of the world’s largest and most glamorous companies are pouring money into energy-storage technology, with building users set to benefit from a technical revolution spearheaded by the car industry.
At the same time, renewable power is accelerating and transforming our electricity mix and national carbon footprint. This summer Scotland met its entire electricity needs for one day from renewable power, and this milestone has already been reached several times by Germany and Portugal. Latest UK Government energy statistics show that renewable energy is rapidly replacing coal as the main source of electricity generation
25% of total UK electricity generation was from renewables last year, which was a 29% rate of increase compared with 2014. Wind power was responsible for almost half. Meanwhile, coal generated just 22% of the country’s electricity — down from 30% in 2014 — making 2015 the first year that renewables accounted for a larger proportion than coal.
UK electricity demand has also dropped by 6% in the past three years as the energy efficiency of appliances and systems has improved. Heating and cooling technologies in buildings are playing their part, with upgraded replacement systems delivering energy savings of 25% to 40% and payback times of five to 10 years.
The rapid decarbonisation of the Grid also makes a powerful argument for wider deployment of heat pumps, which might have previously been shunned by some specifiers because they use electricity as their prime energy source. Adding a reduced carbon ingredient to their inherent Coefficients of Performance (CoPs) will make an increasingly persuasive case — particularly for users who also take advantage of the Renewable Heat Incentive (RHI) payments they should now attract if the Government follows the feedback it has received from the industry to the RHI consultation.
Upgrading the envelope of a building through improved thermal insulation and airtightness can, it is true, deliver even higher savings — over 50% — but with longer paybacks of 24 to 28 years. However, a real step change that can dramatically cut these payback periods will be the roll out of fully integrated, whole-building solutions combining energy efficiency and renewables — augmented by energy storage.
Solar and wind power are, by nature, intermittent energy sources and often not available in sufficient quantities at the times best suited for buildings. If you can capture renewable energy during the day when demand is low (and electricity prices at their cheapest) for use at peak evening and early morning periods when the user would normally have to pay the highest tariff then you have the recipe for a sustainable, balanced grid and much lower prices for consumers.
By storing renewable energy when demand is low for use when demand is high, you quickly reduce strain on the Grid and increase its capacity to meet the country’s needs while also cutting its costs. And you make possible the concept of a 100% renewable Grid.
At the same time, the cost of the lithium-ion batteries used to store renewable energy is falling and is predicted to drop by more than 60% by 2020. The cost of flow batteries should fall by around 40%. Suddenly energy storage is becoming a realistic prospect for a much wider user base. Payback on small-scale systems is estimated at around 10 years — and falling.
Suppliers are rolling out 7 and 10 kWh batteries for connection to domestic solarPV systems. By making energy storage affordable to more users, the industry is starting to look at the prospect of buildings operating ‘off-grid’ and becoming, in effect, energy islands with an unprecedented level of energy security.
However, as the adoption of energy storage accelerates, there will be considerable technical and practical hurdles to overcome. That’s where the building engineering services industry comes in.
The technology at either end of the system is evolving fast, with ever-more-efficient methods for collecting renewable energy and the growth of ‘smart’ methods for measuring and monitoring usage. It will be the task of the specialist engineer to provide the expertise that glues it all together and makes it work in practice.
This is a whole new world for building energy systems, and storage is a highly disruptive technology. Initially, and for some years, fault levels will be high and there will be a steep learning curve.
New technical standards in development include ‘IEC 60364-8-2: Smart low-voltage electrical installations’, which will ultimately form part of IET Wiring Regulations. It lays down basic requirements for connections of renewable-energy systems, associated loads and electrical storage to existing grids and requires systems to be adequately protected. Work on technical standards for the different types of battery is also underway.
The Grid is already displaying systems of ‘stress’ caused by such a radical change, and it will struggle to cope with multiple distributed systems
Engineers will have to work hard on ensuring Grid stability, voltage control, active and reactive control, frequency control, load-shedding capability and different strategies for dealing with remote storage.
Building-services specialists will find themselves in the role of ‘integration engineers’ as they use their skills to put all the pieces of this new jigsaw together. This includes the growth in ‘smart grid’ and greater inter-connectivity, with end users still needing the capability of switching between central Grid supply and local power networks.
It is a major technical challenge, but one that has the potential to change our energy landscape for generations to come. In the meantime, it will provide lucrative and fulfilling work for the integrators — those building-services engineers willing to take up a new challenge.
Tim Rook is technical director of the Building Engineering Services Association (BESA).
