Low carbon, resilient cities and campuses

An increasing number of international delegations visit Denmark to study the efficient low carbon urban heating and cooling solutions in our cities. They find it interesting, that little Denmark has city-wide district heating, that almost all the CHP potential is utilized, that all waste is utilized 100% for energy and not least that innovative solutions like preinsulated pipes, large-scale solar water heating and large thermal storages are developed in Denmark.

Most cities from other countries have difficulties to plan and implement similar solutions, but the campuses can. Naturally, because campus owners want to find the best and most cost-effective solution for the whole campus including the buildings. Like Danish city councils, they want to plan the best solutions for their urban area.

A good example is the university campuses and the military campuses in the US. Several delegations have visited Ramboll in Denmark to be inspired and we have several assignments to help them.

Therefore, Denmark has an important role in the new IEA project, EBC Annex 73, Towards Net Zero Energy Public Communities, http://www.iea-ebc.org/projects/project?AnnexID=73

Ramboll is partner in the Danish consortium, which has been funded by EUDP in a 3-year project, and we are also participating in the US group of experts in the project. In April 2017 we organized a workshop in Copenhagen and worked on the application for the project.

Shortly after approval of the project, we had our first conference for exchange of experience in Washington DC, December 6, organized by the Energy Branch of US Army Corps of Engineers in co-operation with IDEA.

It was very inspiring for all of us, and I learned the importance of a new criteria for successful planning and design. Energy systems shall be not only low carbon and cost effective, but also resilient.


Happy Energy New year 2018. There is a global need for sustainable urban energy solutions

After a break I find it is time to continue my blog on sustainable urban energy solutions.

I can find at least the following three reasons:

Global awareness: The year 2015 was a global milestone. September 2015 UN agreed on the 17 sustainable development goals to transform our world. Developing sustainable energy solutions in cities have a positive impact on at least 3 of the goals: No. 7 Affordable and clean energy for all, No. 11 Sustainable cities and communities and No. 13 Climate action. December 2015 we finally got a formal climate agreement after a successful COP21 in Paris. Moreover it seems that these goals and the agreement has started a movement in the right direction, not only among most member states, but also among many leading cities and campuses.

Danish action. Already in 2012 the Danish Parliament agreed that the climate goal for Denmark is to be independent of fossil fuels in 2050. But how to do it in a cost effective and sustainable way? Based on several studies, the Energy Commission submitted a comprehensive report April 2017. The main recommendations are: that wind energy should be the dominating renewable energy source for Denmark and that the challenge will be: not to establish enough wind energy, but to utilize this fluctuating and unreliable energy source in an integrated energy system. Due to economy of scale, we know that sustainable urban energy solutions will be a main driver for establishing such an energy system in cities including the 4 energy carriers: electricity, district heating, district cooling and gas grids.

Denmark is a show case. Denmark has for decades been recognized being a frontrunner in the green transition, in particular within district heating and wind energy. We have in Ramboll strong experience in planning and implementing these technologies in Denmark and internationally and are pleased to present this experience. We have noticed that the number of study tour delegations we have hosted has increased in 2017. Not only from Europe, but from more than 15 countries all over the world. In 2017 we have also experienced an increasing market for our consultancy services in many countries. This indicates that many countries, cities and campuses have started to take action on the UN sustainable development goals and the Paris agreement.

The blog. In 2018 I will try to update my old blogs and continue with more interesting aspects of sustainable urban energy solutions. Please also look at http://www.ramboll.com/energy and https://stateofgreen.com/en/profiles/ramboll


Two Energy World Records in Vojens



















The town Vojens is known all over the world for Vojens Speedway Center, starting with Ole Olsen, world champion several times.

Today Vojens is also known to be the solar city number one. The local consumer-owned district  heating company Vojens Fjernvarme is in 2014/2015 in the process of establishing the world largest, 70,000 m2, solar heating plant and the world largest, 200,000 m3, underground thermal seasonal heat storage in an old sand pit.

Both records is a factor two larger than the next largest. However, the record will not last long, as several similar projects combining solar and seasonal storage are in the pipe line. Soon the this storage technology may also store surplus useful heat from industries and waste-to-energy plants, which else would be wasted.

The huge storage will be operated as an interseasonal heat storage allowing the solar heating plant to deliver more than 50% of the annual heat production to the network. The rest of the heat will be produced by 3 gas engines, a 10 MW electric boiler, an absorption heat pump and gas boilers.

The storage is excavated in an old sand pit. The 200,000 m3 water volume will be seperated from the district heating water by a heat exchanger. A huge “plastic bag”, formed by a special welded plastic liner, will ensure that the water does not dissapear into the sand and remain clean. The surface of the water will also be covered by the liner and moreover an insulated cover and draining system to remove rain water.

The maximal temperature is in principle 95 dgr. C, but it is planned not to be much higher than 80 dgr. C in order to prolong the life-time of the liner.

On the picture we see that the most of the liner is installed and that the pipe construction for warm inlet on top and colder inlet in the bottom is under construction.

Ramboll has in the design introduced several improvements based on experience from the previous smaller pit storages.

Special attention is paid to:

  • protection of steel pipes against corrosion
  • keeping the water clean without organic material
  • damaging the insulated cover
  • installation of the liner
  • production of process water

The cost of heat in winter from the solar heating combined with the interseasonal heat storage is competitive against the heat from gas boilers, due to economy of scale.

The plant is purely commercial without any subsidies except the indirect subsidy in terms of energy tax on gas.

The solar plant is almost completed, and the pit almost filled with treated water. We hope that the storage pit will be ready when the sun starts to shine and warm up the panels this summer.

For more information, contact Flemming Ulbjerg fu@ramboll.dk




The Hidden Backbone of the Liveable City

Ramboll Hidden back bone in the liveable city


Imagine you are standing on a green roof top. You can-not see, hear or smell any sign indicating how the energy is generated and what happens to waste water and waste. Only in the distance you notice some activity in an industrial area. In the farm land there is no landfills, no poluted rivers and no power plants. Instead the farmers produce surplus straw and wood to be processed at the large energy plants in the outskirts of the city.

What is the secret ? Very few know it and it is difficult to explain. It is my experience that one simple picture can explain more than a big report, and thousand numbers. Therefore I got the idea to this picture, showing a little but important corner of our “liveable city” and how it interacts with the farm land and the rest of the world through markets for electricity, gas and other fuels delivered by ship.

It is a challenge to create liveable cities. Cities, which are not only sustainable, but also worth to live in. In such a city we take it for granted that all energy and environmental services are carefully planned and implemented to be efficient, environmental friendly and not least cost effective. The more cost effective the more money we have available for our national and private budgets and thereby increasing our welfare.

In our vision of a liveable city, the energy infrastructure is a hidden back bone of the city. Thanks to this infrastructure for electricity, district heating, district cooling and natural gas, hidden below the ground, you cant see, hear or smell any sign of energy production. The urban area reserved for human activity.


  • The power grid supplies all buildings, except remote islands and transmits mainly renewable electricity from wind turbines and CHP plants to the buildings.
  • The district heating grid delivers surplus heat and renewable heat to all buildings in the city, whereas buildings outside, which are too expensive to supply with district heating are supplied with individual heat pumps and building level plants.
  • The district cooling grid supplies efficient cooling to buildings in the city center, to commercial buildings and to institutions, also limited by the criteria of cost effectiveness.
  • The gas grid supplies the power plants and industries with process energy.


Thus the energy grids have the same importance as water and waste water in modern cities.

Thanks to the grids for energy and environment the plants, which produce our energy and solve our environmental problems can be allocated in certain areas dedicated for this activity and benefitting for the synergies among them.


  • The waste water treatment plant delivers biogas to the gas grid and the sludge incineration plant heat to the grid.
  • The waste incineration plant use all waste, which can-not be recycled, to generate heat and electricity to the grids.
  • The CHP plant generates electricity and heat to the grids based on gas, coal and an increasing share of biomass.
  • The district cooling plant generates cooling and heat to the grids based on electricity or it generates cooling based on surplus heat in the district heating grid.
  • The hot water storage optimizes the heat production day to day or even longer
  • The cold water storage optimizes the cooling production and reduces the need for installed capacity
  • The cooling plant could include an aquifer storages for cold and warm water and there could be access to sea water cooling
  • The district heating could have access to deep geothermal heat.
  • The industries, which have process energy consumption, could use all the energy services or they could deliver surplus capacity and energy to either district heating or district cooling.

Our buildings have of course to be energy optimized with a good in-door climate and be able to use low temperature district heating and high temperature district cooling.


As a result we can use our green top floors and enjoy a view to other green and read roofs without any chimneys and other appliances. Only in the distance we can observe some tall stacks with white clean smoke and rotating wind turbines indicating where our energy services are generated.

Economy of Scale – the Secret of Sustainable Energy Solutions

The “Triple E” container ship

A few weeks ago Maersk presented the world’s largest ship to the public in Copenhagen. This very impressive container ship, which can load 18,000 containers, is of the “Triple E” class. Triple E stands for Economy of scale, Energy efficiency and Environmental improvement. According to Maersk, the CO2 emission of transporting 18,000 containers in this magnificent ship is as low as 3 g/ton/km, whereas it e.g. is 47 g/ton/km for a truck, which can carry around 3 containers. In other words, 6,000 times larger cargo reduces the cost by a factor 15.


The same “Triple E” principles are known from  the energy sector

A similar “Triple E” principle can be found in several of our energy technologies for cities. The more densely building stock and increased demand of concentrated energy in cities open for more cost effective, energy efficient and environmental friendly technologies. I can think of at least 3 significant ones.

Triple E” district heating pipes.

If a small building which has a heat demand of 100 MWh/year are to be supplied by a cheap heat source 1 km away, it will be very expensive. The small 25 mm pipe, which has the sufficient capacity, may cost up to 10,000 DKK/Km/MWh/year. In case the demand is 6,000 times larger, equal to 600,000 MWh/year, the cost of the required 600 mm pipe will only amount to 50 DKK/km/MWh/year in similar conditions. Thus, an increase of a factor 6,000 reduces the cost by a factor 200. The energy efficiency and environmental performance seem to be the same. The larger district heating system you have, the more energy efficient and environmentally improved heat sources you may be able to explore.

Solar heating

Solar water heating is the most efficient way to catch the solar energy. It can roughly catch 70 times more energy per Ha than e.g. corn, however the cost of solar heat depends very much on the size of the plant. The cost of heat from a 3 m2 plant at a single family house is at least 1,400 DKK/MWh, whereas the cost of solar heat from an 18,000 m2 large plant is only 200 DKK/MWh. Thus, an increase of a factor 6,000 reduces the cost by a factor 7. The energy efficiency and environmental performance will not change much.

Biomass boilers

Biomass, such as straw and wood, have been important energy sources ever since we managed to control the fire. Unfortunately, individual stoves and boilers for single family houses are inefficient and emits harmful emissions. However, by increasing the size by a factor 6,000 going from e.g. a 20 kW boiler supplying a single family house to a 12,000 kW boiler plant supplying a district heating system, the efficiency may increase by a factor 2 and the emissions may be reduced by a factor 100 or more. The price per kW will not change much.

Find more inspiration at http://www.stateofgreen.com/en/Profiles/Ramboll


What makes solar energy cost effective

The sun it the most reliable renewable energy source we have, but how can we use it in a cost effective way ?? And what is solar energy ?? and is solar energy cost effective ?? 

When you google or read about solar energy it seems that the majority agree, that solar energy is coming from solar panels or solar PV cells, producing electricity.

If you analyse the costs of this solar electricity you will soon find out, that it  is far more expensive than electricity from other renewable sources connected to the grid, e.g. large wind turbines. However for off-grid installations providing the consumers with 12 V electricity for LED lighting and low energy electronics they are unique. So the answer today is both a no and a yes.  In the future we may hope for a double yes.

But what about solar hot water panels?

Hot water panels are standing in the shadow of the solar PV, almost forgotten, and mainly known as solar hot water panels for single family houses. These small panels on the roofs are not cost effective in urban areas in which we can produce the hot water much cheaper with surplys heat and renewables via district heating. However, they are very successfull on the roofs of single family houses in e.g. Southern Europe and China. So also here the answer depends on the conditions.

The newest development is however large-scale solar water heating plants based on large efficient panels. The solar energy provided as hot water up to 90 dgr.C from such plants, typically larger than 10,000 m2 of panels is very cost effective and competitive against oil at world market prices. The plants are booming in Denmark to supply district heating networks, but almost unknown in most other countries. In Chile the first very large plant for the mininig industry is under construction.

What makes them cost effective ?

The secret seems to be that they are optimized with the aim to be competitive. Therefore they are simple and efficient and the benefit from the large scale effects. The larger fields, the more cost effective up to around 20,000 m2. Also the heat storages, which level out the solar heat during some days are much more efficient and cost effective in large scale. The only precondition for using these cost effective panels is that you have a corresponding large demand for hot water in the summer months, which you have in district heating systems and e.g. in some mining industries.

One more advantage with the large solar heating plants is that they are monitored, proving that they are really cost effective, see e.g. the links below for further information.



 The picture shows the 18.000 m2 solar heating plant at Marstal Distric Heating, Ærø, Denmark. Left below you see the first 10.000 m3 test underground hot water pit storage.






Aarhus and Copenhagen – Energy Efficiency Landmarks for Europe

The EU directives for Energy Efficiency and Renewable Energy request all regional and local authorities to integrate district heating and cooling into the urban planning. Moreover the Energy Efficiency directives request that new power capacity should be located neat market, which can utilize the surplus heat and reduce cooling losses.

This is a challenging “hen and egg problem”. You cannot use the surplus heat and RES without district heating and it is difficult to develop the capital intensive district heating infrastructure without the cheap efficient heat production from power plants.

We have solved this problem in Denmark. There are many good cases to study in Denmark, which proves how it can be done. In particular two landmarks, Aarhus and Copenhagen, could inspire large European Cities on how to implement the directives.

The second largest city in Denmark, the City of Aarhus, cultural city of Europe 2017, was the first city in Denmark to develop a district heating plan for the whole city and moreover combined with the first approval two new CHP units at the power plant Studstrupværket.

You may find information about the Aarhus heat transmission system at:


The plan has been fully implemented since year 2000 and is now entering a second phase of increasing the share of renewable energy significantly.

Greater Copenhagen, a region of 20 local authorities, was the first region to implement a regional heat plan including zoning of gas and district heating based on CHP and energy from waste. Moreover the plan was combined with the first approval of a new CHP plant with heat accumulators located at a new site close to the heat market – Avedøreværket. Exactly as it is requested by the EE directive.

You may find more information about the integrated district heating system in the Copenhagen Region below:

Visit the heat transmission company CTR who owns the eastern part of the transmission system:


Visit the heat transmission company VEKS, who owns the western part of the transmission system


Visit the waste management company Vestforbrænding, who owens the northern part of the system


Visit our Ramboll profile at Stateofgreen.com and find a presentation of the whole system among our related media:


Denmark has taken the lead again
No doubt many European cities will catch-up with Denmark and reach the same level of urban energy efficiency within some years, however Denmark takes one more step. The policy of transforming the whole energy sector to be independent of fossil fuels will be a challenge to the energy systems and the building sector to be even more energy efficient and integrate low quality and fluctuating renewable energy.

We can already now see how the challenge boosts a development of more efficient supply of district heating, e.g. integrating all possible heat sources and storing heat for longer time in huge heat storage tanks.

Avedøre CHP plant in Copenhagen – a landmark for other cities – the first large CHP plant located at a new site close to the heat market according to national energy legislation.

2012 a remarkable year for European Energy Efficiency

All EU countries can benefit from 35 years of Danish experience to implement the new EU energy directive from 2012, and in 2012 Denmark started a new road map toward CO2 neutral heat and power in 2035.

I can see two reasons that year 2012 was a turning point in European efficiency towards a more sustainable energy sector in Europe and in particular in Denmark – and these two reasons are linked together.

The first reason is that 90% of the Danish Parliament March 2012 entered an energy policy agreement regarding the first steps up to 2020 on how to bring Denmark on the right track towards independency of fossil fuels. In fact, spokesmen from the political parties agree that the overall objective is that the heat and power sectors shall be (net) independent of fossil fuels in 2035, and that other sectors should follow not later than 2050. It will be a challenge to do it in a cost effective way, not to reduce welfare but on the other hand to increase competitiveness. http://www.ens.dk/en-US/policy/danish-climate-and-energy-policy/political-agreements/Sider/political-agreements.aspx

The second reason is that the European Community agreed during the Danish presidency in 2012 on a new Energy Efficiency Directive – the European Law on Energy Efficiency. It was finally published 25 of October 2012. http://ec.europa.eu/energy/efficiency/eed/eed_en.htm

The this directive forms together with the Energy Performance Directive for Buildings and the Renewable Energy Directive a perfect packet of European Energy legislation, which will minimize the fossil fuel consumption in buildings in a cost effective way. The objectives of the building directive are to improve the indoor climate in a cost effective way taking into account local conditions. Moreover buildings shall be nearly zero carbon emission building taking into account the opportunity transferring renewable energy and surplus heat from the power production (CHP) to buildings via district heating and cooling infrastructure. To facilitate that, national, regional and local authorities, according to article 14 in the EE directive expected to plan for urban heating and cooling infrastructure in order to identify where it is cost effective to develop it. Even more, the EE directive requests that all new power capacity shall be located near the heat markets and be designed to supply both heating and cooling, unless it is not cost effective. The logic in this request is that the fossil fuel consumption for heating can be cut down by around 70% by using heat extracted from large power plants compared to heat only boilers, thus reducing the losses in cooling towers.

And how are these two reasons linked?

They are linked not only because the Danish Ministry of Energy Managed to help the Commission with the directive, but because Denmark already is on the right track towards a low carbon community and that the Danish Experience since 1980 in least cost development of district heating based on Renewable Energy and CHP is a model for other European communities on how to implement the directive.

In fact, thanks to the heating infrastructure, which already has been developed to supply 63 % of the population with low carbon clean heat, and the energy efficiency improvements in buildings, Denmark has the key to further improvements.

We have many good cases to study in Denmark, but in particular two landmarks, Aarhus and Copenhagen, could inspire large European Cities on how to implement the directives. The Avedøre CHP plant (picture) was the first power plant to be located at a new site near the heat marked in accordance with the new legal framework.

In my next blog I will give more information on our two landmarks.


Smart Energy Cities

The world population is increasing and has now exceeded people. The need for good indoor climate and hot sanitary water is increasing even more.


Unfortunately, the world will run short of fossil fuels within a few generations, and we have to reduce climate gas emissions due to the risk of climate change – not to speak about the security of supply for future generations.


At the same time, more and more people prefer to live in cities. Cities grow and new cities develop.

This is a challenge, but also an opportunity to serve the population with the necessary thermal services in a smart and sustainable way. In smart energy cities low-carbon energy in general can be provided in a more cost effective way to buildings than in remote areas.

Continue reading “Smart Energy Cities”

Smart Cities have Smart Backyards

A view from the city centre to Amager and Amagerforbrænding

Local politicians and urban planners know about the NIMBY (Not In MY Backyard) Syndrome:

  • Everybody wants to benefit from efficient urban infrastructure, such as waste water treatment, waste treatment, and Combined Heat and Power production (CHP).
  • Nobody wants to see, smell or listen to the plants, which are vital for these services. They should be located far away in the countryside in another municipality, and definitely not be located in one’s own backyard.

A view from the city centre to Amager and Amagerforbrænding

Most city authorities prefer not to have new CO2 emitting coal-fuelled power plants near the city, but appreciate electricity from coal-fuelled condensing plants far away. If cities will not host the last generation of coal-fuelled power plants in Europe, they will be situated far from cities and operate as inefficient condensing plants (45% efficiency) instead of efficient CHP plants (90% efficiency).

Many city authorities also refuse to process the waste in the city and thereby miss out on the opportunity of using all the energy potential.

According to the EU directive for Renewable Energy Sources (RES), the proposal for Energy Efficiency (EE) and according to the EU Energy Efficiency Plan 2011, Smart Cities are however, supposed to develop cost-effective smart grid infrastructure for electricity, heating and cooling.

Moreover renewable energy plants and CHP plants are supposed to be located near or in the cities in order to transfer renewable energy and surplus heat to the buildings. Thereby the buildings can be nearly zero carbon buildings in the most cost-effective way in accordance with the EU Directive for Energy Performance of Buildings. If we exploit these opportunities, there will be more resources for social welfare.

Seen from social sustainability perspective, smart sustainable cities should take care of their own infrastructure in their own backyards and not impose their waste and power plants on other municipalities.

But how do we improve public acceptance of large energy producing and waste processing plants? World class environmental protection standards are not enough; we need more.

Urban- and Architectural Design in Copenhagen

The solution is urban and architectural design to form a more socially sustainable city design.

In urban planning, the usage of the city districts in Copenhagen is regulated:

  • Most districts are for the citizens.
  • A few districts are for heavy industry and city infrastructure – let’s call them city backyards.

Such city design increases public acceptance of e.g. large CHP, waste-to-energy plants and peak boilers. They are almost the only visible installations, which indicates that more than 60 million m2 of the heated floor area in the Copenhagen Region is supplied with efficient heat from the integrated city-wide district heating system

Good architectural design will also increase public acceptance, and the plant in the backyard could be accepted as a natural part of the city skyline and even become a monument of the city. The minor budget increase following from good design can surely be justified compared with the alternatives.

In Copenhagen we have two good examples:

The Avedøre CHP Plant at Avedøre Holme was the first power plant in Denmark and maybe in the world which, in accordance with national energy legislation, was allocated at a new site – at a strategic location in order to serve the near-by heat market. The alternative would have been heat only boilers in the city and a low efficiency condensing plant far away and more long high voltage transmission lines to the city.

Avedøre CHP plant at Avedøre Holme

Please find more information from DongEnergy


and from Ramboll Power


The plant is located in the industrial area of Avedøre Holme in a suburb of Copenhagen. The district also hosts a slag deposit and a waste water treatment plant. Recently, also large wind turbines have been added.

Initially, there was some resistance from the local authorities and citizens, but as the architectural design of the building has turned the plant into a kind of monument, the acceptance has increased.

Another example is the waste-to-energy plant of Amagerforbrænding in the northern part of the island Amager. The site also include a coal-fuelled CHP plant, a biomass CHP plant, a waste water treatment plant, a sludge and biogas treatment plant, a geothermal plant, wind turbines and city gas production and storage facilities. The city district at Amager also allows space for wind turbines.

The city district at Amager also allows space for wind turbines

According to the proposal from the Danish architect, BIG-Bjarke Ingels Group, the roof of the Amagerforbrænding’s new waste-to-energy plant will be formed as a ski slope on a “Hill”. It seems that the Hill will be even more impressive than the roof of the opera house in Oslo.




Magic in Reykjavik

In Reykjavik the urban heating infrastructure is a one-pipe district heating system based on geothermal energy from a CHP plant in the mountains. The challenge has been to find an acceptable solution for the location of four large steel tanks for hot water storage on the top of a hill in the city.

With a little magic they have disappeared and turned into a “Pearl”.

The tanks are located in a circle and form part of the wall in a huge circular building, “The Pearl” used for exhibitions and trade. On the top there is a circulating restaurant offering a view of the city. The rest of the wall is glass and a fifth tank, which is hollow, hosting the Saga Museum.



More information about Design and Architecture

For more information about architectural design as a mean to integrate urban heating in the city environment, you can find interesting papers in issue no 3/2011 of the HotCool magazine on district heating and cooling from DBDH. Among the papers are more information about the Pearl and the Hill at Amagerforbrænding.