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.






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.




European Energy Efficiency legislation adopts 35 years of Danish experience.

A cornerstone in the coming EU Energy Efficiency Directive is to develop the district heating based on Combined Heat and Power (CHP). Local authorities shall develop heat plans and power companies shall install new power capacity with CHP near heat markets. This is what we have been doing in Denmark with great success since 1980. Ramboll has taken part in this development at all stages and is ready to transfer the experience to the rest of Europe. Continue reading “European Energy Efficiency legislation adopts 35 years of Danish experience.”

Off shore wind farms – an urban energy solution ?

Off shore wind farms

Off shore wind farms

Can off shore wind farms be an urban energy solution ? and what has the Island Samsø and Copenhagen in common ?

The Island Samsø is the first Island in Denmark to be net independent of fossil fuels (on annual basis) – and hundreds of energy experts from all over the world have travelled to Samsø to learn  how did they it and see with own eyes

I will mention 3 important factors :

  • The co-operation between the people to develop efficent and smart solutions, not least district heating and wind farms
  • District heating in uran areas based on the available low carbon sources
  • Off shore wind farms financed by  local people

Thereby the heating in the towns have become CO2 neutral and the electricity production from the wind exceeds the remaining energy consumption for power, heating and traffic. Taking into account that the energy value of electricity is larger than the value of fuels, it is even more than CO2 neutral, however the wind is fluctuating, so the island is still dependant of the power grid.

Copenhagen has a vision to be net independent of fossil fuels in 2025. This vision is mainly based on the same factors.

Copenhagen has already 98 % of all buildings connected to the district heating grid and a large share of the production is already based on waste and biomass CHP. Therefore it will possible to be 100% independent for the heating sector within a few years. Bicycles, public transport and electric cars will also help, however there will still remain a demand for fossil fuels and not least for electricity.  Therefore investments in off shore wind farms in the Baltic Sea near Copenhagen will be an obvious solution. Although Copenhagen is not yet  independent of fossil fuels, the efficient district heating in the region and the bicycles have inspired many visitors in the past 25 years.

Off shore wind farms are in fact one of the most obvious and cost effective CO2 neutral urban energy solution – for two reasons:

  • It is the most cost effective solution for producing electricity based on renewable energy and it would be many times more expensive and even impossible to produce the same amount of electricity with building level wind turbines or solar cells.
  • The district heating and district cooling including storages, CHP plants and large heat pumps will help to integrate the wind energy in the energy system

This is probably the two most important features of the “intelligent power grid”, namely

  • that it can transfer renewable energy from “near by” wind farms to supply buildings  in urban areas and
  • that the district energy system is the most “intelligent electricity consumer”.

Have you been on a virtual energy study tour ?

At www.energymap.dk you can visit many interesting energy cases on a virtual tour. You are welcome to visit our profile http://www.energymap.dk/Profiles/Ramboll to study our urban energy solutions, cases and projects. Once you have decided what you would like to study in detail, you may consider to come to Denmark and see it real.

See also www.dbdh.dk  www.euroheat.org and www.districtenergy.org for more information about urban energy solutions.

Continue reading “Have you been on a virtual energy study tour ?”