Since concentrated solar collectors can deliver higher flow temperatures with higher efficiency compared to standard collectors such as high performance flat plate (HPFPC) and evacuated tube collectors, they are of interest for heating networks with supply temperatures above 100 °C. In addition, they can usually track the sun, which can increase the solar yield over the course of a day.

In this paper, different collector technologies and their properties are described. In addition, concentrated and non concentrated collectors are compared with each other on the basis of their Solar Keymark characteristics and in a simulation study for implementing in district heating systems.

The comparison and simulation of high performance flat plate collectors and parabolic trough collectors for heating networks shows that at higher network temperatures, parabolic trough collectors deliver higher yields at German locations. The parabolic trough collectors (PTC) investigated are especially interesting at locations with high direct radiation, as this can be better reflected and converted into heat than diffuse radiation.

This work is part of the German research project Pro-Sol-Netz, funded by the German Federal Ministry for Economic Affairs and Climate Action (BMWK). Pro-Sol-Netz aims to develop and evaluate technologies for the integration of parabolic trough collectors in district heating (DH) and process heat.

<p>For large-scale solar district heating plants, there is often the choice either to provide solar heat to on-site&nbsp;consumers or to feed it into a district heating grid. Plant operators get a better price if they sell the heat to the&nbsp;on-site consumers instead of to the grid. Current state-of-the-art control strategies typically decide on the basis&nbsp;of temperature thresholds on the mode of operation: if the heat should be stored for selling it later to the&nbsp;consumers or it should be fed into the district heating grid. Such strategies, however, can lead to frequent rapid&nbsp;mode switches throughout the day and sometimes the storage is loaded insufficiently, so that heat has to be&nbsp;bought back from the grid. If, the other way around, the storage tank is loaded to a higher extent than needed,&nbsp;this leads to increased storage losses. To address these problems, this contribution presents a predictive rulebased&nbsp;control strategy that takes information on the predicted future conditions into account. By doing so, it&nbsp;ensures that the storage is only loaded to an extend which can be sold to the on-site consumers, thus reducing&nbsp;storage losses, increasing efficiency and maximizing monetary profit for heat sales.</p>

Currently, companies in the solar heating sector may choose from a wide range of tools for modelling and simulating solar thermal power. However, due to the deviant design of some collectors, conventional simulation tools may be inadequate in correctly assessing the performance of such collectors. This study aims to test and validate an in-house simulation model for T160 PTC collectors developed by the company Absolicon Solar Collector AB by comparing measured data with simulated results. A solar district heating (SDH) plant in Härnösand, Sweden featuring 192 parabolic trough collectors (PTC) is used as a case study for the validation. Operational data such as weather data, solar heat production and collector loop/ambient temperatures were collected from the facilities of Absolicon. The data was compiled and simulated using a Python model developed for the T160 collectors. The study shows an acceptable correlation between simulated and measured data during periods with high DNI where a relatively high amount of heat is delivered to the district heating. Deviations are present during periods of low DNI and can be derived from inadequate assessments of heat losses from the piping of the installation in addition to inaccurate measurement data.