Modelling of Wax Actuators in Underfloor Heating Manifolds

Tuule Mall Kull,Jarek Kurnitski,Martin Thalfeldt

doi:10.1051/e3sconf/202124611009

Tuule Mall Kull, Jarek Kurnitski + Show 1 more

Open Access

https://doi.org/10.1051/e3sconf/202124611009

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Abstract

Finding sources for power grid balancing has become increasingly important with more renewables used for production. In buildings, heat pumps could be utilized among other electrical appliances. The heat pumps would work at full power to balance the overproduction in the grid. However, short-term grid flexibility announces the consumption need up to 5 minutes in advance, which can prove a problem to control. When there is no current energy need in the building, all valves are closed. That means that when a heat pump with overridden control starts working at the maximum frequency, its full power heats up the local circuit very fast, especially when there is no storage tank. Whether the heat pump overheats and cannot be used for balancing the grid or the whole system opens for heating depends on the regulating valves and their opening speed. For underfloor heating systems, the valve opening speed is slower than for other systems as wax actuators are used. This paper focuses on how to model these wax actuators and determine the opening time to provide input for further studies on flexibility. A physical and a linear segment model are parameterized and the results show that the wax actuator fully opens the valve in six minutes.

Highlights

Power grid that is rich in renewable energy, faces an increasingly difficult challenge of ensuring the grid power frequency at the needed 50 Hz level
That means that when a heat pump with overridden control starts working at the maximum frequency, its full power heats up the local circuit very fast, especially when there is no storage tank
This paper focuses on how to model these wax actuators and determine the opening time to provide input for further studies on flexibility

Summary

Introduction

Power grid that is rich in renewable energy, faces an increasingly difficult challenge of ensuring the grid power frequency at the needed 50 Hz level. The frequency stays constant when production and demand are in balance. It can be faster and cost-efficient to change the demand rather than switch on or off other production sources. Large consumers such as factory lines are a logical option. As the building sector consumes 30 % of electrical energy globally [1], buildings cannot be omitted as a possible flexibility source. It could be possible to switch household electrical appliances, but the increasing use of heat pumps allows using thermal energy storage in buildings to balance the power grid as well [2]. Several control methods have been developed to utilize either the storage tank or structural thermal storage in buildings for flexibility [4]

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