Electric avenues

EDGE London Bridge balances demands of grid with occupants’ needs. Credit: EDGE London Bridge

There is at last a sense of urgency that the climate crisis is upon us and we need to decarbonise our lives – and soon. This is not an issue that can be solved easily, but there is a broadly accepted global vision for a zero-carbon built environment that depends on two key strategies. Firstly, a big reduction in demand on the energy network through efficiency improvements and optimisation and a complete stop to the burning of fossil fuels. Next, a decarbonisation of the energy supply through an increase in the use of zero-carbon and renewable energy.

This methodology is known as the ‘Paris Proof’ and it demonstrates that a high-performance built environment is vital to achieving a net-zero carbon economy, while showing the need to drive fossil fuels out of the mix.

This all-electric ‘revolution’ has come about because of the dramatic reduction in the emissions from grid-supplied electricity. The graph below illustrates that, since 2018, UK grid power has, on average, been more carbon-effective than gas due to the significant reduction in the use of coal and the increase in large-scale photovoltaics (PV) and wind energy installations.

The new generation of all-electric buildings need to be designed to assist in the management of the supply, demand and storage equation in the future, essential because the main zero-carbon sources, wind and solar, are not always available and the demand on the grid is highly variable, as illustrated in the snapshots below. With the limitations on renewable capacity it is inevitable that the carbon intensity will be at its worst when the peak demand is highest, as this is when the coal power plants come online.

Designers have a significant role to play in minimising the peaks and troughs in demand by flattening the demand curve where we can through low-carbon design, load management and energy storage, both thermal and electric. Read on to find out how.

The changing balance of the grid, 2011-2018 and going towards 2050. Credit: Carbon Intensity API, National Grid ESO in partnership with Environment Défense Fund Europe, University of Oxford Department of Computer Science and WWF.
The changing balance of the grid, 2011-2018 and going towards 2050. Credit: Carbon Intensity API, National Grid ESO in partnership with Environment Défense Fund Europe, University of Oxford Department of Computer Science and WWF.

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NEED TO KNOW: DESIGN TIPS FOR ALL-ELECTRIC BUILDINGS

Challenge design briefs – oversizing of building systems is endemic in the industry. As well as being carbon intensive it leads to operational inefficiency for the life of the building.

Design more defensively to minimise the peak demands on building systems. Managing solar gain and heat loss are time-honoured ways of achieving this. External shades, blinds and shutters are still viewed as ‘exotic’ in the UK when they are widely used across Europe. They really help to drive down peak loads and resource use on many levels.

Use thermal mass storage in its many forms to flatten and shift the demand curve away from the peak. This could be in concrete, in the ground, in ice tanks or in buffer vessels.

Use heat pumps where possible and avoid using direct electric resistance heat as a primary thermal source for air or water. It is expensive and still ultimately wasteful of our limited resources. Prioritise the integration of PV power generation onto roofs and even vertical surfaces. When the sun shines we need to make the most of it.

Design the electrical systems to respond to external signals including real-time carbon emissions, cost or energy so that the load can be manipulated to suit the availability of renewable energy in the grid.

Consider the integration of domestic or commercial scale battery storage to further facilitate load shifting and reduce the need for additional generating capacity. In the United States, the renewable energy contribution has grown from 9% to 18% over the last 10 years and there has been a surge in building-level distributed energy systems, many incorporating an element of battery storage, and the Tesla Powerwall is showing a very rapid uptick in adoption after a slow start five years ago, with over 200,000 units sold.

Demonstrating strategies for energy management: WWF Living Planet Centre. Credit: Morley von Sternberg

The design of the WWF Living Planet Centre in Woking, Surrey (with Hopkins Architects, 2012), shows how some of the strategies described can be implemented. The building design used significant external shading and mass in several forms to minimise the peak loads. Exposed concrete soffits and phase-change materials in the timber roof provide thermal mass. Earth ducts in the ventilation systems minimise fresh air loads. Energy piles beneath the building store energy inter-seasonally with electric water-to-water heat pumps providing heating and cooling. PV panels on the roof meet some 20% of the regulated requirements and the overall peak energy demand is some 40% lower than a conventional office.

For buildings we are designing at London Bridge (with Pilbrow & Partners) such as the EDGE, our approach has been to assess and design for the constantly varying relationship between the building (demand), distributed energy sources (on-site supply and storage) and utility grid (off-site supply) to create long-term low carbon impact.

All-electric buildings are here to stay. They bring new challenges, but also provide an opportunity to create cleaner and healthier cities and places while achieving the big objective – a net-zero world.

Patrick Bellew is the founding director of environmental engineer Atelier Ten

ALL-ELECTRIC HOUSING

The move away from the familiar gas boiler to electric heating either directly or by heat pump-based thermal energy systems is a very significant one for the design of residential projects.

Electricity has become lower in terms of carbon emissions, but it is still significantly more expensive than gas. Direct electric space and water heating is inexpensive as a first cost but will be increasingly expensive for home-owners to use.

A heat pump needs a source of heat (either air or water) to drive the process, and this has space and noise implications, particularly with the air-based systems that require an outdoor unit to operate.

Water-based heat pump systems offer an alternative that allows energy to be moved between multiple occupants and user types, and that can offer efficiencies as well as access to alternative energy sources or heat sinks, such as groundwater.

NET-ZERO ALERT!

With the availability of green/renewable power purchase agreements, it is possible to label a building as “net-zero” when it is all-electric simply by the purchase of green power. Indeed, it is becoming the new norm to do so. We need to be careful not to allow poorly performing buildings to use this as a label to support unearned virtue.

Tracking and benchmarking the Energy Use Intensity (kWh/m2) of our designs and projects remains a vital indicator of the first of the Paris Proof objectives and this needs to be enforced through Building Regulations.