• Energy Research

The concept and methodology of a magnetocaloric heating network is proposed. A small thermal network consisting of several magnetocaloric heat pumps (MCHP) is considered from the point of their scaling and connection properties. We found a linear scaling law following the heating power variation with AMR mass, which can be included in an MCHP lookup table produced by a 1D transient AMR model. To estimate the performance of networks with different number of MCHPs, a set of single MCHPs coupled through temperature boundary conditions are modelled and network formulas are applied for the reference case of Gd packed beds. A performance optimum is found for specific design points compliant with building heating applications.

Abstract This paper proposes a new flexibility management method which can offer incentives to flexibility service providers so that they are encouraged to actively participate into the congestion management of distribution grids. The proposed method consists of a three-stage market clearing method and three types of flexible block offers: flexible demand bids, flexibility service offers, and energy arbitrage blocks. These cover most of the needs of flexibility providers. These flexible block offers are more efficient in terms of computation burden in comparison with the other flexibility offers in the existing literature. Flexibility prices are specified in these flexible block offers, which can guarantee a certain level of rewards for the customers who can help in the congestion management process. Case studies on a modified Roy Billinton Test System demonstrated the efficacy of the proposed flexibility management method for managing congestion and encouraging customers to provider flexibility services.

The definition of overall district heating network performance indicators is under-investigated in the literature. This study reviews existing methods of performance estimation and develops a convenient methodology for an array of district heating networks applied to a Danish case study. Performances of the networks with state-of-art pipe transmission coefficients are compared to older traditional pipes using an effective average approach. The reported efficiencies and analysis of contributing factors show, that a single parameter is not sufficient to compare large-scale district heating systems and a multiparametric analysis must be employed. The effective average total heat transmission coefficient is evaluated based on the Technical Evaluation Factor and a multivariate regression is performed on typical sets of network parameters: pipe type, pipe series, pipe age, and operational temperature. The developed methodology is applied to testing an array of geographically independent district heating networks, pointing to possible performance bottlenecks, and discussing potential remedies.

AbstractNon-convex scheduling of energy production allows for more complex models that better describe the physical nature of the energy production system. Solutions to non-convex optimization problems can only be guaranteed to be local optima. For this reason, there is a need for methodologies that consistently provide low-cost solutions to the non-convex optimal scheduling problem. In this study, a novel Monte Carlo Tree Search initialization method for branch and bound solvers is proposed for the production planning of a combined heat and power unit with thermal heat storage in a district heating system. The optimization problem is formulated as a non-convex mixed-integer program, which is incorporated in a sliding time window framework. Here, the proposed initialization method offers lower-cost production planning compared to random initialization for larger time windows. For the test case, the proposed method lowers the yearly operational cost by more than 2,000,000 DKK per year. The method is one step in the direction of more reliable non-convex optimization that allows for more complex models of energy systems.

Abstract The main goal of the ENOVHEAT project is to develop, build and test a prototype of an innovative heat pump based on active magnetic regenerator technology. This device can be coupled to a ground source heat exchanger and an under-floor heating system to provide for the space heating needs of a low-energy house in Denmark. However, the use of a simple controller leads to modest performances because the heating system is running mostly part-load. This numerical study has tested the possibility of using heat storage in the indoor environment and building thermal mass as an effective strategy to improve the operation of the magnetocaloric heat pump. Indoor temperature set point modulation can take advantage of the building energy flexibility potential to maximize the full-load operation time of the heating system and therefore improve its seasonal COP. Results show that this control strategy can significantly increase the seasonal COP, ranging from 2.90 to 3.51 depending on the building thermal mass. Although the indoor temperature stability is reduced, it allows the magnetocaloric heat pump to reach energy use efficiencies which are similar to the ones of conventional vapour-compression heat pumps.