Solar assisted heat pumps

Solar Assisted Heat Pumps have the potential to provide low carbon heat for domestic hot water generation and low temperature heating. They have advantages over conventional solar thermal systems because they can generate heating and hot water during periods of low or zero solar, whist still maintain the advantage of not needing to be connected to the gas grid. They are simple in nature and can be installed in a wide range of applications. They are also currently uncommon in the UK so a thorough understanding of the operating performance and characteristics is required. This is potentially an important energy technology that can be used to reduce heating energy consumption and reduce CO2 equivalent emissions in buildings. The paper describes the technology and presents an investigation in an office application. It describes an experimental investigation of solar assisted heat pumps which gives the relative performance compared to conventional methods

Investigation of an integrated low carbon solar assisted heat pump

© 2016, International Institute of Refrigeration. All rights reserved.Solar Assisted Heat Pumps have the potential to provide low carbon heat for domestic hot water generation and low temperature heating. They have advantages over conventional solar thermal systems because they can generate heating and hot water during periods of low or zero solar, whist still maintain the advantage of not needing to be connected to the gas grid. They are simple in nature and can be installed in a wide range of applications. They are also currently uncommon in the UK so a thorough understanding of the operating performance and characteristics is required. This is potentially an important energy technology that can be used to reduce heating energy consumption and reduce CO2 equivalent emissions in buildings. The paper describes the technology and presents an investigation in an office application. It describes an experimental investigation of solar assisted heat pumps which gives the relative performance compared to conventional methods

Estimation of Cooling Energy Demand and Carbon Emissions from Urban Buildings using a Quasi-dynamic Model

Global warming and the urban heat island effect in large towns and cities demand new approaches to cooling buildings in an efficient and sustainable way. Modern refrigeration, air conditioning and heat pump (RACHP) systems can achieve a high coefficient of performance and low emissions, but refrigeration technology already accounts for around 15% of worldwide electricity use and up to 10% of all greenhouse gas emissions, so in the context of international agreements to reduce global greenhouse gas emissions by up to 80% RACHP systems alone cannot provide a sustainable cooling solution for cities. The purpose of the model described in this paper is to provide a simple and easy to use tool to estimate the impact of different heating and cooling technologies, alternative building design and operating parameters and future global warming, on the energy demands and carbon emissions of buildings. Existing software tools for analysis of buildings can provide high quality results for a given scenario, but the determination of an optimal solution demands multiple simulations, which can be time consuming and require post processing to interpret the results. The Excel based tool uses a quasi-dynamic energy balance model and reduced weather data set to generate rapid results, allowing the user to view the building’s temperature profile, energy demands and carbon emissions in near real time and to develop an optimum cooling strategy. Results are presented for a single building version of the tool. When fully developed, it will allow the user to model clusters of buildings in an urban environment

Magnetic Attraction

In the 2015 United Nations Climate Change Conference, COP 21 in Paris, world leaders have been negotiating to limit the global warming to below 2°C by 2100. These talks are necessary to avoid serious climate catastrophes and reduce greenhouse gas emissions by increasing the use of zero carbon technologies such as magnetic refrigeration for heating or cooling. This is an emerging, innovative and potential low carbon technology. Due to the increased concern about global warming and an ever increasing energy consumption, the interest in magnetic refrigeration as a new heating or cooling technology competitive to conventional vapour compression has grown considerably over the last 15 years. The principle of magnetic refrigeration is based on a phenomenon known as magnetocaloric effect (MCE). This was discovered by Emil Warburg in 1881 and is related to the property of some exotic materials such as Gadolinium and Dysprosium that heat up when applying a magnetic field and cool down when the magnetic field is removed

Life-Saving Cooling

Large areas of many developing countries have no grid electricity. According to the International Energy Agency’s (IEA) World Energy Outlook (2015) report, 1.2 billion people lacked access to electricity in 2013, which is equivalent to more than 16 percent of the world population. The research reported by IEA (2015) showed that more than 95 percent of those living without electricity live in rural areas, mainly in sub-Saharan Africa and developing Asia where there is no distribution grid for electricity, and there are no prospects of the grid reaching them in the near future see Figure 1. Even in areas with grid power, the demand for electricity has outpaced supply resulting in unreliable electricity availability, insufficient for continuous refrigeration

The Value of hybrid heat pumps

In households not connected to mains gas, electric heat pumps offer the opportunity to provide high efficiency low carbon heating as an alternative to electric heaters, LPG or oil based systems. As a result this technology is an ideal heating solution for the 4 million households in the UK that don’t have access to mains gas. However, electric heat pumps also offer large scale carbon savings when used for heating in the 22 million households that do have gas as well as mains electricity. In these applications hybrid heat pumps present an attractive opportunity for reducing fossil fuel consumption. In March 2013, the Department for Energy and Climate Change (DECC) published a document entitled “The Future of Heating: Meeting the challenge”. This report predicted that by 2030 approximately 26% of the UK’s heating energy output will be met by air source heat pumps alone, and as much as 56% will be met by hybrid system

Simulation of the heat recovery use of R744 systems in a supermarket

This paper describes the outcomes a research project that investigate the improvement in the COP of an enhanced booster R744 refrigeration system that provided MT cooling for chilled food cabinets and LT cooling for cold room/frozen food cabinets by recovering the heat rejected and using it more for other building services applications in the supermarket. For instance, the heat reclaimed can be used for heating, HWS or to drive absorption chillers, either in whole or in part. To demonstrate the potential of the heat reclaimed within the supermarket and its impact on the store’s CO2e emissions, a feasibility study has been performed to examine the innovative system compared to of the existing conventional system which will cover the cooling demands of an existing supermarket. In order to achieve this, the data collected by a smart energy monitoring system will be used to examine the working of the novel system when covering the cooling demands of the store. The energy consumption of the novel system will be analyzed according to thermodynamic theory. Using an Excel model, the potential heat reclaimed will be mathematically investigated for best practice applications of heat recovery. The energy saved and CO2e emission reduction achieved in apply the novel system will be determined and analysed

Evaluation of Supermarket Energy Use and Emissions with Various Technology Options

In this paper, an operational supermarket in the UK has been selected to be modelled by the previously developed supermarket energy simulation software ‘SuperSIM’. Detailed information of the supermarket and model development procedures are explained. The model was previously validated through comparisons with site measurements of space air temperature and humidity and energy consumptions. It is therefore used to simulate, quantify and evaluate supermarket energy performance at various technology options in terms of heat recovery from refrigerant discharge, high efficiency condensers and evaporators and store locations etc

Control strategy of a novel dry air ground source (DAGS) system

Based on a number of studies carried out; it has been identified that Ground Source Heat Pump (GSHP) systems are widely used as one of the preferred low carbon technologies in the UK. The use of these systems is due to their economic advantages and potential reduction of carbon footprint. However, a number of the studies have highlighted that the systems are either installed incorrectly or operated and controlled improperly and therefore result in poor performance. GSHP performance is affected by the temperature of the ground and when thermally saturated its efficiency reduces significantly. This paper investigates the potential to reduce the level of thermal saturation by rejecting heat via a Dry Air Cooler (DAC) when the ground and ambient temperatures favour this. DACs are often fitted to GSHP systems to reject heat during extreme conditions to protect the system, rather than improve performance. In this investigation, an empirical Transient System Simulation (TRNSYS) model has been developed and used to investigate the control algorithms so as to identify the optimal operation and control strategies for DAGS system for enhancing the system efficiency. Specifically, the paper investigates the effect of using a DAC in conjunction with a GSHP system. This includes investigating the (i) energy input into the GSHP system, (ii) ground temperatures and (iii) Coefficient of Performance (COP). The results show significant savings can be achieved

An investigation of refrigerant leakage in commercial refrigeration

Given that refrigerant demand is set to rapidly increase, long term solutions for leakage prevention are required to effect change in the industry. This paper presents the results of a project which investigated refrigerant leakage within two of the UK’s major supermarket chains. Leakage data from 1,464 maintenance records were analysed. The analysis categorized the type, location of each leak and volume of refrigerant replaced during repair. Over 82% of the recorded leaks were from R404A refrigeration systems, and mainly consisted of pipe or joint failures or a leaking seal/gland/core located in the compressor pack and the high pressure liquid line. It is recommended that the industry focuses on improving design, installation and maintenance of pipework and valves, at the components that most often develop faults to minimize refrigerant leakage