Cities beating the heat

The concrete jungle: hard, impermeable pavements, and the glass, stone and steel buildings which dominate the grey landscape of most cities.

More often than not, it’s trees and other vegetation which are often lacking from the cityscape – a combination that gives rise to urban ‘heat islands’ in which city streets can be several degrees hotter than surrounding areas.

Alternatively, green spaces and water can REDUCE temperatures in cities by shading, because water vapour given off by plants or from water bodies cools the air by evaporation.

By and large, the larger the area of green space or waterway, the greater the cooling effect. That was the finding of an international study that included the UK Centre for Ecology and Hydrology (UKCEH) which was carried out as a part of the UKRI-funded RECLAIM Network Plus.

It’s also why a number of cities across different continents — Athens in Greece, Miami in the United States and Freetown in Sierra Leone — have created a new position of chief heat officer to develop initiatives to increase cooling assistance to communities and promote targeted solutions such as tree cover to address urban heat.

By 2100, the urban heat island effect could warm cities around the world by as much as 4.4°C on average, according to the findings of a group of international researchers published in Nature Climate Change in January 2021. This is nearly triple the Paris Agreement objective to limit the global temperature rise to no more than 1.5°C.

Currently, half of the Europe’s total energy consumption is dedicated to heating and cooling, with nearly 80%¹ derived from non-renewable sources, often fossil fuels. With the majority (70%) of Europe’s population living in urban areas², growing urbanisation will further escalate the demand for both heating and cooling.

As cooling itself is a contributor to emissions locally and at a global level, so scaling up while simultaneously decarbonising its energy use will be essential.

District cooling

One largely untapped sustainable resource for cooling cities is district cooling, in which chilled water, transported through insulated pipes from a central source, provides cooling to a district or group of buildings. This is the approach adopted in our latest E.ON ectogrid installation – the UK’s first – at the Silvertown development (pictured below) in East London’s Royal Docks.

Cooling sources can vary from cold water from lakes, seas and rivers to waste cold and heat brought to the necessary temperature with a chiller, a type of heat pump.

Like district heating, district cooling makes most sense in densely populated areas. District cooling is often combined with storage, so an excess capacity of chilled water during the night, for instance, can be stored for use during the day. Another benefit is that, unlike air conditioning units, district cooling does not eject waste heat.

Environmental choices

Not all solutions need to use electricity though. Urban design and natural solutions have a massive role to play. Whether that is redesigning buildings to make use of reflective surfaces, increasing green spaces as heat sinks within cities and even moving industrial centres away from population centres to remove sources of heat in the first place.

One example is the Bosco Verticale building in Milan – incorporating 21,000 trees into a pair of residential tower blocks in the Italian city – that can be copied with areas dedicated to greenery and planting trees in the ground or vegetation on rooftops.

According to the US Environmental Protection Agency, green roofs can be up to 20°C cooler than conventional ones during the daytime, helping to reduce building temperatures, cut overall energy use and reduce peak energy demand.

Enter E.ON ectogrid

There are many ways to solve city heating and cooling in a simple way, but it does not mean basic approaches can’t be improved. E.ON’s ectogrid solution adds intelligence to the concept of district cooling.

Like other district cooling systems, E.ON’s ectogrid™ uses water to cool buildings, but instead of the energy flow being a one-way street from generation to consumption, ectogrid has intelligent controls to share supply and demand of heating and cooling across buildings – thus ensuring any energy use takes advantage of what’s available elsewhere before new energy is generated and fed into the network.

Systems like ectogrid™ can act as giant batteries, storing excess energy when available and discharging when demand is high, helping to manage peak electricity demand by shifting heating and cooling loads to off-peak hours, reducing strain on the grid.

Alongside the Silvertown development, E.ON ectogrid™ is already being delivered at the Milan Innovation District on a former Expo site and in Lund, Sweden, where ectogrid™ is already providing district heating and cooling across Medicon Village, a life sciences research park.

1. eurostat: Heating and cooling from renewables gradually increasing
2. Our world in Data: Urbanization