Results from the Danish research project CITIES demonstrate that surplus wind and solar energy can be used to heat indoor swimming pools, thereby reducing CO2 emissions by at least ten per cent.
The Danish holiday period is in full swing, leading many to flee cities for holiday houses located in smaller coastal towns. Given that Danish summers are typically characterised by fluctuating temperatures, many of these holiday residences are equipped with indoor swimming pools that can be enjoyed rain, hail or shine. The downside is that heating these pools is both costly and has a negative impact on CO2 emissions accounts. However, new results from the national research project CITIES can revert this trend. Over the last three years, researchers from the Technical University of Denmark have developed and tested a method in which surplus production of wind power and solar energy is utilised to heat the water in 30 holiday homes with pools in the seaside towns of Blokhus and Blåvand, which are located on Denmark’s west coast.
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The study has shown that CO2 emissions can be reduced by at least 10 per cent by heating the water when the electricity is generated by wind turbines and stopping it when the electricity comes from sources with a higher carbon footprint. As the water retains the heat for an extended period, holiday home guests cannot notice the CO2-related control of the heating. This difference also has a positive impact on the houses’ electricity bills, which can be reduced on average by EUR 1,400-2,000 (DKK 10-15,000).
“We generally see quite a nice cost-saving potential for the individual homeowner and tenant, as well as a significant climate impact reduction from the new smart heating of the holiday homes with pools, and such control can also contribute to a more stable electricity grid in the future,” says Professor at DTU Compute Henrik Madsen, Research Director and Centre Manager for Smart Cities Accelerator and Project Manager of CITIES.
The holiday homes lettings agency NOVASOL—which has provided the contact with the 30 holiday homeowners—also sees great potential in the method:
“I think that it’ll be increasingly important to the guests which climate footprint they leave. And with this solution, families can drive to the west coast of Jutland instead of flying south, and even use less CO2 because the water in the pool is heated when there is excess green power. When hourly settlement is introduced in Denmark in 2020 and electricity will become less expensive in off-peak hours, it’ll also be a clear economic gain for the homeowner to heat the water at night,” says Thomas Kieldsen, Group Business Development Manager at NOVASOL.
Understanding the optimal time to heat swimming pools via sensor boxes
A CITIES-developed sensor box in the holiday homes communicates with a central server established with ENFOR A/S in order to calculate the optimal time for heating the swimming pool’s water, which lead to the aforementioned CO2 reductions and savings on electricity bills.
This optimisation is achieved in a partnership with Tomorrow a/s in which forecasts of the CO2 levels in the electricity are obtained for the coming days. These are then compared with an ENFOR-based prediction of heating needs. The predictions are based on weather forecasts, information about temperature requirements, and other data which are downloaded directly from a server with booking information at NOVASOL. The central server at ENFOR thus gives the individual house notification to start the heat pump or electric cartridge.
“Communication via the mobile network has been found not to be very reliable, and—in the future—we’ll probably use internet connections such as fibre which are now common in the holiday homes,” says Henrik Madsen.
“But we’ve learnt that a relatively simple control of electricity consumption through CO2-related prices works quite well. And the project shows that it is possible to solve some of the balance and voltage challenges that the electricity grid is facing with increasingly more wind power. The next step is to convince politicians that the new energy taxes must be linked to the current CO2 content in the electricity,” he says.
Optimising the capacity of the electricity grid
The actual SmartNet project received funding through the EU’s H2020 funding programme, which concluded 30 June this year. However, the parties have agreed to continue the partnership under the auspices of Denmark’s new research centre for green transition Center Denmark’s ‘FED’ project—Flexible Energy Denmark—which Innovation Fund Denmark supports with DKK 30 million.
The purpose of FED is to ensure that the flexibility of the electricity grid is activated and to help us learn more about how Denmark can best balance production and consumption in the green transition, so that the electricity grid capacity is utilised as optimally as possible.
All flexible electricity-consuming units in Denmark can be controlled concurrently through Center Denmark—including the heat pumps in the holiday homes managed by NOVASOL—but the ambitions go beyond this, explains Henrik Madsen:
“The expectation is to disseminate this CO2-minimising control system to more holiday homes and to the many district heating plants in Denmark, where the water in the district heating pipes can probably provide the flexibility necessary to ensure a very high share of wind power and solar energy in Denmark.”
Giving holiday home rental agencies a competitive edge
NOVASOL is very satisfied with the project:
“As a company, we would never have started up something like this if we hadn’t received help from the DTU engineers, as it takes a lot of computer technology and mathematical algorithms (machine learning),” says Thomas Kieldsen.
In terms of branding, NOVASOL hopes that participation in the research projects will benefit the holiday homes rental agency. Branding may also be a factor for the holiday homeowners, as no one has declined to participate in the project.
“One can well imagine that—in future—guests will choose the house in which the CO2 impact has been significantly reduced compared with the neighbouring holiday homes if the rent and location are roughly the same. Holiday homeowners would never individually be able to establish a solution like the one they’ve received through this project,” says Thomas Kieldsen.
Background information: CITIES – Center for IT-Intelligent Energy Systems in Cities
The Danish goal of a 100% renewable energy system by 2050 has created a need for research that can support the transition from fossil fuels to a modern society, adapted to sustainable energy systems. CITIES covers a wide range of research activities that facilitate the flexibility of the entire energy system by researching efficient, integrated and intelligent energy solutions.
The activities in CITIES cover all aspects of the energy system, including electricity, gas, district heating /cooling and biomass, and most importantly, research into methods to predict, control and optimize their interactions by using advanced IT solutions.
In CITIES, eight Danish and Swedish cities and municipalities, 24 Danish and Swedish industrial partners and 15 international knowledge institutions from the EU, China and the USA participate. The project is partly financed by Innovation Fund Denmark.
Photo: Michael Oxidine, Unsplash