Heating in EU households accounts for 79% of the total energy consumption. In cold climate areas, like Finland, the percentage is even higher. Enermix set out to test how room-level control in district-heated apartment houses would affect the comfort of living and energy consumption.
“Our mission is to digitalize Finnish buildings, especially the existing ones,” says Janne Heinonen, the CEO of Enermix, a Finnish tech company. “We focus on existing buildings because the owners are still reluctant to invest in smart building solutions during construction because of the additional costs they entail. Another reason is that there’s not fierce competition in making old buildings smart.”
Enermix has developed Talotohtori Building Management System, a cloud platform to which you can connect building automation systems and IoT devices, vendor-neutrally. Talotohtori services include indoor conditions monitoring and analysis, remote building automation control, smart heating control, and energy consumption monitoring.
Heinonen found out about KIRA-digi, a national digitalization program, and saw an opportunity to test out an idea about smart heating control in apartment buildings with district heating. The pilot project got funding and then started in May 2018. The experiment ended in December 2018 and provided interesting results for building owners.
Aiming at Better Indoor Conditions and Energy Efficiency
Finland is among the leading EU countries for district heating penetration, alongside Denmark, Estonia, Lithuania, Latvia, and Bulgaria. Around 65% of Finland’s district heating energy is already generated from non-fossil sources, and that proportion will increase in the future.
The challenge with any central heating solution in an apartment building is that residents cannot control the indoor temperature individually. Neither can they get a separate heating bill as the cost is distributed among all the apartments in the building.
The Enermix project team wanted to test if apartment-specific heating control would help achieve the following goals:
- Improve comfort in individual housing units
- Achieve energy savings
- Reduce peaks in heating energy consumption
The Test Ground
The project carried out tests in three apartment buildings constructed in the 1990s and early 2000s and owned by the Y-Foundation, a rental housing provider. Air temperature and humidity sensors were installed in 50 spaces and 11 apartments were equipped with smart, maintenance-free radiator thermostats.
“To my surprise, when we surveyed the residents, less than 10 percent of them were interested in controlling the indoor temperature individually,” Heinonen mentions.
The experiment required software and algorithm development from Enermix. They also added the ability to control smart thermostats on the cloud platform. In addition, they developed a mobile app for residents to control indoor temperature. Another tech firm, APinf, provided a platform for sharing sensor data from the experiment openly through an API.
Some Finnish building owners have installed water consumption meters for each apartment. That way, they can charge each household exactly the right amount for their water use. In contrast, heating costs are predominantly charged by total square meters of an apartment.
Enermix originally intended to devise a formula for a consumption-based distribution of heating costs. Unfortunately, the six-month period of the experiment was not long enough to allow developing a fair charging plan.
The experiment demonstrated that it is possible to use IoT and cloud services to control heating individually in each room in a district-heated building. “Even some professionals doubted whether you could adjust the temperature to your liking in two adjacent rooms because heat is transferred via the separating walls,” Heinonen explains. “But our test proved otherwise; we could measure differences of two to three degrees Celsius between rooms.”
Measurements during the test gave some interesting data about the conditions in the apartment buildings. For example, they revealed temperature differences between apartments as high as seven degrees Celsius. Dealing with such a high variation clearly requires action from the building owner, such as a need to rebalance the radiator network. This, however, was out of the scope of the experiment.
As a result of using Talotohtori’s services and its smart algorithms in the project, there was a 5% saving in district heating costs during the test period. The peak power required was diminished by 20 to 30 percent, resulting in direct cost savings. To be able to optimize heating to such an extent, Talotohtori used both sensor data and weather forecasts.
Users of the mobile app were able to give direct feedback on the experiment; although, the project received too few comments to allow drawing definitive conclusions about resident satisfaction. Nevertheless, Y-Foundation reported that they received less temperature-related complaints than usual.
The Way Forward
“Our service keeps the average temperature at the required reading very accurately. Y-Foundation aims at 21.5 degrees Celsius, and thanks to our real-time control, we can deliver it within a 0.3-degree variance,” says Heinonen. “Whether that is the ideal temperature for every resident, is another question.”
According to studies, the variance between what people think of as a comfortable temperature is up to six degrees. Pleasing everyone in one building or apartment is therefore always going to be a challenge. Heinonen thinks that even reaching a 90% satisfaction level is unrealistic, and that a 60% satisfaction level would be more reachable.
The experiment proved that individual temperature control with smart thermostats can be offered without compromising the overall energy efficiency. To allow this, building owners need to invest 300–400 euros per apartment. The payback time is around five years with an ROI of 5–10%.
“If we think of energy efficiency alone, our service provides the same results without the need for hardware investment,” Heinonen reminds. “However, we are likely to offer the smart thermostat as a next-step option in our services.”