Design of an electrical instant hot water heater for a solar water heating system

Abstract

Solar water heating (SWH) systems have a widespread usage and application in both domestic and industrial sectors. According to the Renewable Energy Policy Network data (2010), 70 million houses worldwide were reported to be using SWH systems [1]. According to (REN21) Renewable Energy Policy Network data (2013) a total 223GWh were potentially produced from 92 million solar water heaters installed [2]. The increase of 22 million units mainly came about due to the fact that China has invested in about 16 million systems. This does not necessarily mean energy savings or reduction in electrical usage for the following reasons. One reason could possibly be that before the installation of the system the user was using less hot water (for cost reasons for example) meaning that little or no energy was previously being used. Another reason could be that the previous commonly used technology employed another size of storage tank, thus limiting the amount of hot water available. Solar water heating is not only environmentally friendly but also requires minimal maintenance and operation costs compared to other solar energy applications. SWH systems are cost effective with an attractive payback period of 2-4 years depending on the type and size of the system. Extensive research has been performed to further improve the thermal efficiency of solar water heating. This dissertation presents a detailed review exclusively on the design aspects of the electrical element of the SWH systems. The first part provides a consolidated summary on the different developments of various electrical elements to heat up the storage tank of the SWH & explain their performances. This project aims to create an alternative electrical element technology for improving the performance of the electric Therefore the innovation will increase the efficiency of a SWH and also increase the added value. In this project the product was tested at various flow rates in respect to temperature conditions. Since the innovation requires more electrical current than stipulated by the IEC 60320 grid electric code for a single device which works on single phase, it is expected that this technology/device will contribute towards saving on electrical energy that is coming from the fossil fuel/natural gas or from Renewable Energy Source (RES). This technology will have a positive effect on the reduction of CO2 and will probably be a very good product for the market. If one had to consider that there are 92 million systems, a mere 1% of which would result in just under one million units. This will have a saving of at least 30GWh of electrical energy annually. The dissertation also explored the effect of the Legionella bacteria both on existing SWH units as well as the proposed innovation. Unfortunately, the current systems used do not protect against this potentially lethal bacteria. The proposed system will be capable of protecting against these harmful bacteria with minimum energy consumption.