The future of urban sustainability is renewable district energy

The by far most important step towards compliance with the Paris Agreement is decarbonization of the production of energy. In the Netherlands, households and industry have been endowed superfluously with endogenous natural gas for more than fifty years, which also was the main source for the production of electricity, together with coal. The availability of natural gas withheld the country to hurry up in the search for sustainable sources of energy. This situation will change dramatically because of the accelerated phasing out of the production of natural gas.

Cities are puzzling how to compensate for the upcoming limitation of the availability of natural gas for heating and cooking. At the same time, they align with sustainability goals. The decentralized production and storage of solar energy, warm and cool water is considered as a main solution of the problem, together with large-scale production of wind energy. The UNEP report District Energy In Cities; Unlocking the Potential of Energy Efficiency and Renewable Energy is an excellent guide and also the source of inspiration, pictures and graphs of this blogpost.

Example 1: Paris

Paris has Europe’s first and largest district energy network, part of which uses the Seine River for cooling. The Paris Urban Heating Company serves the equivalent of 500,000 households, including 50% of all social housing, all hospitals and 50% of public buildings, such as the Louvre Museum. The district heating network aims to use 60% renewable or recovered energy by 2020.

Thermal district energy

Thermal district energy (DES) is a system that supplies thermal energy to multiple buildings via underground pipes carrying steam, hot and cold water.

This type of energy has been applied for years. It has proven to exceed the efficiency of onsite generation of energy (see diagram below) but until recently these systems have been running primarily on fossil fuels.

Modern so called 4th generation systems draw on multiple sources of energy and this enables a stepwise phasing-out fossil sources. Denmark has already reduced its national CO2 emissions since 1990 with 20 per cent due to district heating. A percentage that will grow substantially, although the deployment of district energy has its limitations. Currently, at least 20 per cent of EU-wide district heat is generated from renewable energy sources, hydro-electric energy included.

Example 2: Frankfurt

DES will enable Frankfurt to achieve 100% renewable energy by 2050. Through DES, the city will improve energy efficiency, be able to switch from fossil fuels, use waste heat and provide balancing for variable renewable energy sources.

Fourth-generation systems operate at lower temperatures, resulting in reduced heat loss which makes it feasible to connect to areas with many low-energy buildings. Through heat (and cold) storage these systems are an inexpensive solution for creating the flexibility required to integrate high levels of variable renewable energy into the electricity grid.

The deliverables of district power plants are heating (steam or warm water), power (electricity) cooling (water) and the storage of all. Traditionally, these plants focused at combined production of heat cooling and power. All energy sources available kept moving turbines to produce electricity followed by second – or third-stage heat capture. In case of a surplus in heat, water can be heated and stored in boilers. Heat is also collected from industrial process from saline water from underground reservoirs and from sewage, to be conversed by heat exchangers and heat-pumps. The same sources can be used for cooling if conversion takes place by Integrating absorption chillers. Available for cooling are free available sources like cold water from oceans, lakes, rivers, aquifers and waste cool, to be conversed by heat exchangers. District cooling has huge potential to reduce soaring electricity demand from air conditioning and chillers. In addition, it reduces consumption of environmentally damaging refrigerants.

Example 3: Dubai

In Dubai, air conditioning represents 70% of electricity consumption. This led the city to develop the world’s largest district cooling network, which by 2030 will expand to meet 40% of the city’s cooling demand. District cooling is halving Dubai’s electricity use for cooling and also reducing its consumption of fresh water through use of treated sewage effluent.  

The figure below is summarizing the sources of a 4th generation district station, in comparison with older factories. The balanced use of available sources is a cornerstone of energy policies in Denmark and Germany.

The role of local government

Local government is uniquely positioned to advance district energy systems because of its capacity of planner, regulator, facilitator and large consumer of energy and providers of infrastructure and services as well. Local governments worldwide are using a wide range of policies and activities to promote district energy, demonstrating these roles.

The majority of business models for district energy involve the public sector to some degree, and in many cases the public sector has partial or full ownership of the project.

Helsinki’s Katri Vala heat pump captures heat from the city’s waste water.

‘Hybrid’ public and private business models have many faces:

  • a public and private joint venture where investment is provided by both parties that are creating a district energy company, or where the public and private sector finance different assets in the district energy system
  • a concession contract where the public sector is involved in the design and development of a project, which is then developed, financed and operated by the private sector during one or more decades.
  • a community-owned not-for-profit or cooperative business model. In this model, the local authority takes on a lot of risk initially in development and if it underwrites any finance to the project.
The number of full private business models is limited.

A large solar thermal plant with heat storage connects to a district heating network in Brædstrup, Denmark.

The need for mapping demand and supply

In most countries, the Netherlands among them, are ample opportunities for deploying district energy. The requirements are medium to large concentrations of citizens and the availability of waste or waste water and sufficient supplies of underground water. The first step is making detailed maps of all resources at one hand and the demand for heat and cooling at the other hand.

Mapping has been valuable to target spending for energy efficiency programs, identify areas of the city with high peak demand, and test the cost and benefit of local energy supply versus large transmission projects. An excellent example of such an inventory is the Boston Community Energy Study: Exploring the Potential for Local Energy Generation, District Energy, and Microgrids (2015).

This mapping exercise used a simulation designed by MIT, in order to estimate the energy demand. Than the local supply was mapped.  The authors of the atlas expect that this information will stimulate bottom-up initiatives, which will be supported by the community. Earth, water and air are invaluable sources for future heating and cooling, supplemented by a limited quantity of bio-gas. Sun and wind will be the main sources for electricity. Our endeavors have to be focused on the development of all sources at the same time, safe-guarding stable availability of sustainable power for industry and consumers.

Other cities have also been mapping the potential for district energy. Amsterdam has issued an energy atlas[3]. This atlas offers information at neighborhood level, for instance the actual thermal and electricity production, existing and proposed sustainable energy projects, opportunities to connect existing sources or networks, data on building stock and ownership and potential for energy saving.

The Study identified forty-two districts around Boston that are good candidates for Community Energy Solutions based on technical criteria (building location and energy demand) and socio-demographic criteria (critical facilities and affordable housing). Future discussions will consider the state of the existing infrastructure in the area, the costs associated with retrofitting buildings and street excavation, and the willingness of building owners to support Community Energy Solutions.

Other cities have also been mapping the potential for district energy. Amsterdam has issued an energy atlas. This atlas offers information at neighborhood level, for instance the actual thermal and electricity production, existing and proposed sustainable energy projects, opportunities to connect existing sources or networks, data on building stock and ownership and potential for energy saving.

The authors of the atlas expect that this information will stimulate bottom-up initiatives, which will be supported by the community.

Earth, water and air are invaluable sources for future heating and cooling, supplemented by a limited quantity of bio-gas. Sun and wind will be the main sources for electricity. Our endeavors have to be focused on the development of all sources at the same time, safe-guarding stable availability of sustainable power for industry and consumers.

*) This article was brought to you by Professor Herman van den Bosch, Professor at Open University of The Netherlands.

Herman van den Bosch

 

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