District heating scenarios: case Helsinki

by | 20-03-2021 | Energy, Smart society

The City of Helsinki is committed to becoming carbon-neutral by 2035. More than half of the city’s heating is produced with coal and the heating system’s emissions account for more than half of Helsinki’s total emissions.

To spur some good ideas on how to reduce carbon emissions from its district heating system, the city organized the Helsinki Energy Challenge with a one-million euro jackpot. The prize money was divided over four winners last week.

If the future of energy is to be a carbon-neutral one, the trick is to remove fossil fuels from the equation. We know that demand for energy is only going to increase. So where is supply going to come from?

According to WindEurope, an industry organisation representing 400 companies and organisations across the value chain of wind, Europe’s energy system accounts for 75 percent of the continent’s greenhouse gas emissions today.

Half of electricity will be wind-powered

For sure, wind power is going to be huge. WindEurope’s CEO Giles Dickson told me:

“Last year, wind accounted for 16 percent of the overall electricity consumption in the EU 27 and the U.K. The EU Commission wants us to deliver half of Europe’s electricity by 2050. To realise that goal, we’ll see wind energy capacity rising from 220 GW today to up to 1,300 GW.”

Next to wind, hydroelectric power and solar are important renewable energy sources. They all have in common that their output depends on the weather. And the weather tends to change.

Large fluctuations in energy supply to the power grid is undesirable for at least two reasons. First, the grid’s frequency needs to be maintained at close to 50 Hz at all times. This is done by keeping supply in par with demand. If the frequency deviates too much, things will start breaking down and blackout may occur – as happened in Texas recently.

The second reason is that fluctuations in supply relative to demand (which is in itself a fluctuating factor) can cause price instability.

When it’s cold, it hasn’t rained, the sun doesn’t shine and there is no wind, some other power sources than direct renewable electricity are needed.


If it is electricity that we want, and we don’t want to activate nuclear or fossil power production, intermittent energy storage would be great. When it’s windy, wind parks could charge batteries so that this stored electricity can be activated when the weather is fair.

Batteries can be part of the solution, but they have limited capacity. They take relatively much space compared to the electricity they can store.

In Vaasa, a technical proof of concept pilot is underway to show how direct electricity from wind turbines can be converted and stored as hydrogen, to be converted back to electricity when the wind lies down and/or demand increases. This concept has been touted as a holy grail but commercially it is far from viable.

In a panel discussion organized by Vaasa Region Development Company VASEK last week, titled ‘Power-to-X-to-Power System’, Erik Jungner, Director for Product Management at Wärtsilä Energy, said:

“The availability of hydrogen at scale will take ten-plus years, but we can already demonstrate that the technology works.”

We will always have combustion

Hydrogen is also expected, in due time, to become the fuel of choice for combustion engines. Many fossil fuel engines can be retrofitted relatively affordably to run on hydrogen instead. And for a long time there will be use cases where combustion is the preferred energy generator.

Karoliina Auvinen is a member of one of the winning teams of the Challenge, ‘Beyond Fossils’. She has a PhD in Energy Transition Design from Aalto University, is a Senior Expert with the Finnish Environment Institute and an advisor to the Finnish Clean Energy Association. She told me:

“There will always be a need for solid, liquid and gas type of fuels. For heavy traffic, airplanes, and adjusting power in the energy system, you will always have combustion.”

In city heating, however, the best way to store surplus energy for later use is as heat. Auvinen:

“Today, sending electricity to heat storage is a hundred times more affordable than electric batteries or hydrogen. The most cost-efficient solutions include heat pumps connected to demand-response. But that’s not enough to achieve a reduction in CO2 emissions of 80 percent by 2035. You need storage as well.”

And this is of course why storage played such an important role in most of the winning Helsinki Energy Challenge proposals. And heat pumps. (Sea) water heat pumps, air heat pumps. ground source heat pumps, exhaust air heat pumps… heat pumps galore!

Floating islands of sea heat

Rather than creating heat itself, a heat pump extracts heat from one place and moves it to another. As we read on The Renewable Energy Hub, a common example of the technique can be found in refrigerators where the evaporation and cooling of a liquid is used to lower the temperature. In the case of district heating, heat pumps are obviously used to extract heat from the outdoors environment – air, water, earth – and insert that heat into buildings and other infrastructure that requires it.

Although they use a small amount of electricity to run, heat pumps are considered highly efficient and clean because they don’t depend on the burning of fuel to create the heat.

The Hot Heart’ is a system of cylindrical reservoirs in the sea just off the center of Helsinki. It uses electricity from the grid when the price is low to convert electric energy into thermal energy using heat pumps exchanging with the sea. When the price of electricity is high, it pumps stored heat into the district heating system.

One of the extras that make this design speak to the imagination is that four of the ten cylinders have a little tropical island built on top, so that Helsinki citizens and tourists can spend days in the jungle all year around.

Among the partners in the Hot Heart consortium, lead by project agency Carlo Ratti Associati, was Danfoss. Through its Leanheat portfolio, the company markets a range of climate solutions, including equipment and software to optimize heat distribution in district heating and consumption within buildings.

Nano-coated salt and top-notch solar panels

Jukka Aho, Head of Global Accounts and Business Development at Danfoss’ DHS Software Business, told me:

“In the Hot Heart proposal, all the buildings in Helsinki would use the same AI technology to minimize the heating requirement from the Hot Heart by using the thermal capacity of the building structures themselves.”

The walls, the air, even the people and pets in a building contain (and produce) heat. A drop or rise in temperature of 0.2 centigrades basically goes unnoticed to people, but represents a significant amount of energy. Viewed as storage capacity, this energy could be used as a flexible asset in response to the fluctuating (price of) supply.

Smart Salt City’ introduced its patented thermochemical energy storage technology as a new way to temporarily store surplus renewable electricity. The team said its storage media is an abundant, recyclable, energy dense, nanocoated limestone-based material. The material can store energy for substantial periods of time without major thermal loss. When discharging energy, it can produce either electricity or high-temperature steam, making it a potential retrofit for existing combined heat and power plants.

The ‘Hive’ team submitted that with heat pumps, up to 50 percent of Helsinki’s demand for heat can be harvested from the sea and that solar thermal fields, thermal energy storage and district heating grid optimization would complete the solution. Hive envisions building two large solar thermal fields, each with a peak capacity of 25 MW. Consortium member Savosolar claims to produce the world’s most efficient flat plate collectors for large scale solar thermal applications such as district heating.

A technology-agnostic approach

Beyond Fossils’ offered a technology-agnostic approach to the future of Helsinki’s district heating. The team expects that the main new technologies will be heat pumps (hey!) using ground, air, water and excess heat streams as sources. However, rather than speculating on the winning tech, the team proposed an auction system. Said Karoliina Auvinen:

“More efficient new storage technologies and more affordable hydrogen fuel will emerge over the coming years and decades. Therefore we thought that the best investment now is in an auctioning system which ensures that the cheapest clean heat sources will be deployed.”

What we hear is “heat pumps”, “storage” and “optimization”. The pumps are a given because in district heating, they provide the most efficient way to extract and move thermal energy from one place to another. Storage is a must in order to balance fluctuations in demand and (especially) supply. Optimization, with AI and all, is the icing on the cake.

The renewable energy transformation is one of the most exciting opportunities to create a more sustainable planet. How we utilize data and optimize large systems with use of data and artificial intelligence may seem like the icing on the cake today; perhaps not as tangible as cylinders of sea water, tropical islands, pumps, pipes, and buildings.

Yet at RAIN we see an ever increasing role for smart data collection, edge AI data reduction, availability and control across the edge-to-cloud continuum. Many future systems, including our energy system, depend on it.

Data utilization and optimization is the name of the game, and it’s our bread and butter. We talk with organizations every day about the data they use (and don’t use!) to optimize their operations.

Are you considering how your data could improve your business? In our experience, there is often plenty of low-hanging fruit to be had. Together, surely we can figure out where to start. If you’re interested, have a chat with our CEO Henri Kivioja. You can book a call with Henri without any obligation.


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