Modelling and simulation of underfloor heating system supplied from heat pump

© 2016 IEEE. This paper describes thermal capacity and thermal inertia of an underfloor heating system supplied from a heat pump. A MATLAB/SIMULINK based thermal model of the system have been developed and presented with detailed mathematical equations. For this purpose, experimental results and actual measurements are used to model the energy storage and temperatures. The parameters used for the model are temperature, power and energy consumption, time constant and real-time. Hence, this model can be used to find building temperature variations, heat energy production, electrical energy consumption, instantaneous power, coefficients of performance on a real-time scale based on different control strategies used for demand side management. The developed model in SIMULINK includes the effect of thermal storage in the underfloor heating arrangement as well as the thermal mass of the building itself. Heat loss calculations were carried out to develop this model. The paper also employs different control strategies for operating the developed model

Development and validation of detailed building, plant and controller modelling to demonstrate interactive behaviour of system components

As plant modelling becomes capable of more complexity and detailed resolution, new opportunities arise for the virtual evaluation of discrete plant components such as flow control and energy conversion devices, and controllers. Such objects are conventionally developed and tested at the prototype stage in a laboratory environment. Designers now seek to use modelling technology to extend their understanding from limited laboratory test results to full building and plant system analysis. This paper describes the development of a modelling system, using ESP-r, for typical United Kingdom domestic house types with hydronic gas or oil fired central heating including radiator and underfloor heating systems, and with a variety of conventional or advanced control types. It demonstrates the ability of detailed building and plant modelling to reveal unexpected insights into how real control systems perform in combination with other plant items and in different building types, including estimation of their influence on annual energy consumption. Comparisons with measurements taken in test rooms confirm that the observed behaviour of controls is realised in practice. The authors conclude that the complex dynamic interactions that take place between the various elements that make up a real building energy system have an important influence on its overall energy performance, revealing causes of variance that cannot be identified by laboratory testing alone, or by simplistic energy assessment tools

Application of a new dynamic heating system model using a range of common control strategies

This research investigates the overall heating energy consumptions using various control strategies, secondary heat emitters, and primary plant for a building. Previous research has successfully demonstrated that a dynamic distributed heat emitter model embedded within a simplified third-order lumped parameter building model is capable of achieving improved results when compared to other commercially available modelling tools. With the enhanced ability to capture transient effects of emitter thermal capacity, this research studies the influence of control strategies and primary plant configurations on the rate of energy consumption of a heating system. Four alternative control strategies are investigated: zone feedback; weather-compensated; a combination of both of these methods; and thermostatic control. The plant alternative configurations consist of conventional boilers, biomass boilers, and heat pumps supporting radiator heating and underfloor heating. The performance of the model is tested on a primary school building and can be applied to any residential or commercial building with a heating system. Results show that the new methods reported offer greater detail and rigor in the conduct of building energy modelling

Sustainability assessment and performance evaluation of a Ground Coupled Heat Pump system: coupling a model based on COMSOL Multiphysics and a MATLAB heat pump model

The present study investigates the sustainable use of a ground coupled heat pump (GCHP). In order to assess the performance of this type of installation, a computer model composed by two parts has been developed. The Borehole Heat Exchanger (BHE) model is developed in COMSOL Multiphysics, based on numerical methods. Part of the results are fed to the heat pump energy model, developed in MATLAB. A real case study has been used to validate the model: the Faculty of Engineering of La Sapienza University in Latina, undertaking a renewal project for an abandoned part of the building. After the renovation, the building will host a research center on the topic of low-enthalpy geothermal systems. The analysis have demonstrated that the modelled GCHP system can supply a significant share of the energy required from the future research center. This amount of energy can be provided keeping almost stable the thermal balance of the surrounding region in the subsoil, operating in a sustainable way. The range of variation of the ground temperature with respect to the average value is within the limit of 5°C, which is the cap set by the international legislation

Simulation, implementation and monitoring of heat pump load shifting using a predictive controller

A predictive load shifting controller has been developed and deployed in a low-carbon house near Glasgow, UK. The house features an under floor heating system, fed by an air-source heat pump. Based on forecast air temperatures and solar radiation levels, the controller 1) predicts the following day’s heating requirements to achieve thermal comfort 2) runs heat pump during off peak periods to deliver the required heat by pre-charging the under floor heating. Prior to its installation in the building, the controller’s operating characteristics were identified using a calibrated building simulation model. The performance of the controller in the house was monitored over four weeks in 2015. The monitored data indicated that the actual thermal performance of the predictive controller was better than that projected using simulation, with better levels of thermal comfort achieved. Indoor air temperatures were between 18°C to 23°C for around 87% of the time between 07:00-22:00. However, the performance of the heat pump under load shift control was extremely poor, with the heat being delivered primarily by the unit’s auxiliary immersion coil. The paper concludes with a refined version of the controller that should improve the day-ahead energy predictions and offer greater flexibility in heat pump operation for future field trials

The effect of hot water use patterns on heating load and demand shifting opportunities

Heating loads for modern houses are lower than older houses with a larger proportion used to service domestic hot water (DHW). Electric heating systems, e.g. air source heat pumps (ASHP) and underfloor heating, offer load shifting possibilities with solar thermal DHW systems providing further opportunities. Other dynamic effects such as heat loss from water tank and stochastic demand need to be considered too. Hence integrated dynamic simulation is adopted to look at building thermal interactions with explicit plant representation and linked network mass flow and power flow solutions. Stochastic DHW use patterns characteristic of the UK are investigated. Different time controlled heating profiles are simulated to investigate demand shifting. Findings show user behaviour strongly influences water heating requirements, solar DHW system effectiveness and consequentially load shifting potential

Numerical investigation of energy potential and performance of a residential building-integrated solar micro-CHP system

International audienceThe studied micro-CHP unit converts concentrated solar energy into electricity and heat by coupling a 46.5 m² parabolic trough collector with an oil-free single-cylinder steam engine operating according to the Hirn cycle. Originalities of this system are two axis solar tracking and direct steam generation. The exhaust heat of the cycle is recovered to cover building's heat needs, while the electricity is either self-consumed or fed back into the electricity grid. Experimental studies have shown that it is impossible to achieve continuous operation of the facility without an additional heat source. Thus, we are studying solutions for integrating a backup heating system from dynamic thermal simulations performed with TRNSYS© software One of them consists in adding a 30 kW boiler to the primary circuit in order to ensure daily electricity production. However, this is restricted by the considered storage tank. A parametric study on the volume of the storage tank makes it possible to propose an optimal solution for heat recovery. The results indicate that a storage volume of 3 m 3 meets the needs of the building and limits the heat losses due to heat storage. In order to optimize the use of such a micro-CHP unit, a heat sharing between several buildings equipped with 3 m 3 storage seems therefore to be a coherent solution