This work aims at the development and the experimental characterization of new applications for adsorption heat pumps and chillers driven by industrial waste heat or renewable sources that can provide heating and/or cooling. Adsorption technologies offer the advantage of providing heating and cooling from low temperature sources below 100 °C without using refrigerant with high Global Warming Potential and with very low electricity consumption. Therefore, the technology enables the use of large untapped heat sources, increasing the energy efficiency of the heating and cooling sector with very limited impact on the environment. Several applications were investigated numerically for Switzerland using a simplified model of an adsorption heat pump. Four scenarios were identified as interesting: (1) the valorization of low-grade industrial waste heat in district heating networks, (2) energy efficiency improvement of district heating substations, (3) an autonomous adsorption heat pump with a wood pellets burner and (4) cooling applications. These scenarios were experimentally validated with a laboratory test of a commercial silica gel/water machine. Results show that there is a gap of up to 40% between the prediction of the simplified model and the experimental results. Therefore, there is huge potential to improve the performances of this commercial unit for these applications.
In this article the development of a high performance, double-wall vacuum insulated hot water thermal energy storage for high temperature applications is presented. In this concept, the main heat losses of the tank are limited to radiation and to the thermal bridges present in the wall of the tank and fittings. This concept is well suited for high temperature applications such as those found in the industrial sector where storage energy losses are an important issue. Few studies on double wall evacuated tanks were found in the open literature and none fully employed a completely evacuated gap as proposed in this study. A structural analysis was performed to validate the proposed design and ensure conformity to high temperature applications. Heat transfer calculations assessed the impact of low emissivity coatings on the radiative heat transport in the evacuated gap. An evaluation of the investment cost of the novel concept was also performed and comparisons made with conventional insulated TES on the market. A numerical model of the tank was developed and the thermal behaviour investigated under different configurations. An economic analysis presented the investment attractiveness with respect to the common TES alternatives on the market. Overall, the presented concept is clearly viable not only in terms of technical feasibility but also in terms of economic practicality.
New uncovered photovoltaic-thermal (PV-T) collectors were developed and tested to produce electricity, chilled and hot water. The use of uncovered PV-T collectors has already been investigated for heating applications. However uncovered PV-T collectors are also interesting for radiative cooling applications. This concept was already demonstrated in two plus energy houses that participated in the Solar Decathlon Europe competition. The working principle of radiative cooling is to use the radiative heat loss of the collector top surface to cool down a fluid which is then used to air-condition a building This paper focuses on the collector design characteristics and their performances for radiative cooling and heating applications. The procedure for the performance characterization is inspired from the quasi dynamic test method for uncovered thermal collector of the new EN ISO 9806:2014. For the identification of the collector parameters GenOpt has been coupled with TRNSYS. These coefficients are then used to establish the thermal efficiency curves for heating and cooling applications: the results of three different PV-T collector designs are compared between each other and to the performance of an uncovered solar collector.
The FLEXYNETS project on low-exergy district heating and cooling systems has been started in summer 2015 in the framework of the European H2020 program. The project aims to develop a new generation of intelligent district heating and cooling networks that reduce energy transportation losses by working at temperature levels lower than 40 °C. Reversible heat pumps and chillers are used at laboratory scale to exchange heat with the DHC network on the demand side. In this way, the same network can provide contemporary heating and cooling. FLEXYNETS solutions integrates effectively multiple generation sources (including high-and low-temperature solar thermal, biomass, cogeneration and waste heat) where they are available along the DHC network. Two network types are considered in simulation: the classic supply-return type and the single-pipe system. This paper describes possible operation strategies and some control aspects related to the second network type.
This study focus on the integration of solar thermal (ST) systems in the Swiss pharmaceutical industry to provide the thermal energy need for their processes. An analysis of the heat demand in this sector showed that around 2 TWh of heat could be supplied with conventional thermal solar systems, such as flat plate collectors or vacuum tube collectors. To identify the obstacles to integrate solar systems and define appropriate solutions, two case studies were considered to assess the technical feasibility and economic viability of these solutions. The two feasibility studies focused on drying processes. The solar heat supplied to the pharmaceutical processes was estimated using the simulation tool Polysun for both case studies. The solar plant sized for case study 1 produces 617 MWh/year with 1060 m² of solar collector (solar field gross surface) and 50 m³ of storage. Whereas for the case study 2, the heat production reaches 382 MWH/year with 684 m² of solar collector and 30 m³ of storage. Finally, the economic evaluation of the ST systems, based on different offers, shows that the price of the heat produced by the solar thermal system reaches almost twice the price of the gas, which allows to determine the competitiveness of the ST system in both cases comparing to conventional heating systems.
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