How to achieve energy neutrality in cities

This article by Andy van den Dobbelsteen and Nico Tillie first appeared on Reuters The Great Debate UK on Nov 9, 2010.
Andy van den Dobbelsteen is a Professor of Architecture and Nico Tillie is a PhD candidate at Delft University of Technology. Tillie also works for the City of Rotterdam.

This year’s World Town Planning Day, on November 8, was held in 30 countries on four continents. It is a recognition and celebration of the contributions that sound planning has made to the quality of the human environment and provides recognition of the ideals of community planning among the profession and the general public worldwide.

In recent times, World Town Planning Day has been strongly influenced by environmental themes and this year was no different with much of the world’s eyes on the upcoming Cancun U.N. climate change summit. However, our own view is that planners have yet to fully grasp the fundamental question at the heart of the global warming challenge in urban areas: how can cities and towns become far more autonomous and possibly even free from fossil fuels?

In Europe, until now, architects and urban planners have often followed three steps when designing a sustainable built environment. Reducing energy consumption, utilising sustainable energy, and using fossil fuels as efficiently and cleanly as possible. However, to date at least, this approach has not led to substantially more sustainable towns and cities.

As part of a new approach, we have therefore added in another step: re-using waste flows such as waste-water, household and agricultural waste, and residual heat, whilst using renewable energy to satisfy remaining demand. All buildings and urban areas generate "waste streams" that could be harnessed, but rarely are. We believe that adoption of this approach will eventually render the use of fossil fuels completely unnecessary.

Our project is part of the Rotterdam Climate Initiative, which aims to halve the level of CO2 emissions in the city by 2025, compared to 1990 levels. This is an ambitious plan which will require the truly transformational paradigm we advocate in our revolutionary REAP (Rotterdam Energy Approach and Planning) model.

REAP incentivises urban planners to comb urban areas looking for opportunities to exchange energy. For instance, in the area of Rotterdam near the World Trade Centre, many new homes, offices and a second shopping mall and supermarkets are all forthcoming. All of these buildings will have their own heating and cooling needs and produce residual energy flows which can be "exchanged":

*    For instance, supermarkets must continually operate cooling systems which produce huge amounts of heat that, at present, simply disappears into the atmosphere.  Under our plans, heat pumps will transfer this residual heat to nearby homes and buildings.

*    This principle will also allow for the exchange of heat between offices and homes. On hot days, for instance, office air conditioning units roar into action, yet the heat that is produced in this process is currently wasted. It could (and should) be stored, for instance in underground aquifer layers (Heat and Cold Storage) for inter-seasonal exchange (and then used to heat homes during the winter months) or in tanks for covering diurnal or weekly differences.

*    Organic waste from the neighbourhood could also be collected to produce biogas. Moreover, there are also plans underway for the city to generate residual demand for energy using available green technologies such as solar panels or heat pumps.

We applied these principals in Hart van Zuid, an existing district in Rotterdam, where urban planning calls for homes to be built near the Zuidplein shopping centre that can use the residual heat generated by a local supermarket. The Ikazia Hospital, which is located nearby and consumes huge amounts of energy, is also being modified to be energy self-dependent by reclaiming heat from residual hot air and water, while also becoming much better insulated by means of an overarching climate façade which resembles a huge greenhouse covered in vegetation.

While REAP principles can be applied universally, they do require a substantial amount of infrastructure changes. For instance, small communal facilities must be built to store and redistribute energy. Moreover, heat pumps and heat storage systems are needed for counter-balancing daily and seasonal temperature changes.

Logistics also provide a challenge. For instance, suppose a newly built residential complex in a CO2 neutral neighbourhood is completed earlier than the supermarket the residents depend on for their heat. The only interim solution here might be an emergency generator which could prove costly.

However, for all of these potential obstacles, the big picture here is that carbon-neutral urban development is definitely possible, at least for the demand for heat and cooling — as we have evidenced through REAP in Rotterdam. We believe that REAP can be applied in any urban geography and the next step is to see whether it can provide a structure for other natural resources such as water and materials.

While that experiment is for the future, we are extremely excited about the value REAP has right now as a planning tool for urban planners to make the transition from existing city regions to more sustainable and autonomous city regions. Indeed, we believe that adoption of this approach will eventually render the use of fossil fuels completely unnecessary, a development that would be truly transformational.

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