Solar Powered Heating System in the UK
Background
Energy is a critical factor in our lives. Over the years, the need to embrace clean and sustainable sources of energy has increased. For many years people have relied on fossil fuels and electricity for heating water for domestic and industrial use. Fossil fuel was expensive with a lot of adverse effects on the environment, prompting the development of alternative water heating techniques. Advancement in technology has resulted in the development of electric water heating systems. Electricity is a clean source of energy. With the increased population, the demand for electricity went up surpassing the available supply. Many houses that relied on electricity were inconvenienced with constant power outages due to increased demand that resulted in rationing of electric supply to homes. As demand increased, the cost of electric power also went up. Many people could spend a lot on electricity bills which affected their financial wellbeing prompting the research for alternative water heating methods to cut on the energy cost. People tried to heat water directly by exposing it to the sun, which worked well, but not as efficiently as the people desired. The United Kingdom is a developed nation with well-established industries ventured in studies to establish water heating systems that relied on solar energy to heat the water. Solar water heating systems for domestic and industrial uses have been developed over the years.
The sun has been the source of energy on earth for many years. Human beings rely on the sun for energy, both directly and indirectly. The energy sector is one of the most vibrant and critical pillars of the United Kingdom’s economy, hence attracting government and the people’s interest. The nations have realized the need to use energy efficient systems to ensure the available energy is not misused. The United Kingdom is putting measures that will result in a low carbon future and has developed an elaborate energy use strategy that will transform heating, transportation, and change over to smart energy systems. In the recent past, a lot of the United Kingdom’s energy issues can be associated with the sources of electricity for domestic use. The nation is embracing energy policies and practices that will limit the use of nonrenewable energy in domestic premises. For years now, the nation’s reliance on electricity generated from coal-fired systems have continued to decline by government policies advocating for the use of clean energy. Design of United Kingdom houses has also changed with designers embracing approaches that result in better utilization of energy. Today, one of the issues examined before approving the construction of a house is how it relies on green sources of energy and how it can efficiently use the energy available. It has become common to find apartments fitted with solar-powered heating systems in the United Kingdom. There are different types and configurations of solar power. While some arrangements are expensive to design and put in place, some are easy to design and maintain but not very efficient in heating water. Water is a critical resource that supports life, which is required daily for various purposes. This analysis of solar-powered heating system that is common in the United Kingdom, the prevailing weather conditions in the United Kingdom, types of hot water systems and collectors in use.
Key Goals of the Project
Nearly two-thirds of energy consumption in residential areas in the United Kingdom is used for water heating, space heating, or cooling (Jamar et al. 178). According to the Solar Energy Industries Association, billions of pounds are used to pay for the energy spent on water heating and the amount can be reduced if proper systems are put in place to minimize water heating utilizing energy from the grid. The primary aims to encourage the adoption and successful use of solar heating systems in residential areas. With a lot of energy being used for water heating, solar water heating system significantly reduces the amount of energy and finances used in the homes. With the increasing population in the United Kingdom, the demand for electricity is set to go higher, prompting the need to have a solar heating system to supplement existing sources of energy for domestic use (Freeman, Klaus and Christos 607). Solar water heating can also lessen the impact of global warming. Over reliance on nonrenewable sources of energy has been associated with the increase in greenhouse gasses that have severe effects for the environment. Based on energy studies, it has been established that a single family home that relies on a solar water heating system lowers the amount of carbon dioxide footprint generated by the house by up to 30%. In the case of fossil fuel, which is also used for space heating and other activities is eliminated and replaced with solar heating, the amount of carbon dioxide generated by the house needs to be lower than 60 % (Zhai, Yang and Wang 1701). This project, therefore, seeks to lower the amount of carbon dioxide produced by residential homes by reducing the amount of carbon dioxide produced through heating water with energy from nonrenewable sources.
The second goal of the project is to lower the installation cost of solar water heaters. One of the most significant limitations to the adoption of solar water heaters has been the high cost of installation. Many residential houses have failed to be equipped with the domestic solar heating system due to the initial and maintenance cost, which many people are not able to afford (Shirazi et al. 955). This project seeks to identify critical cost centers in the installation of solar water heaters and establish how installation cost can be lowered. With reduced installation cost, more houses will adopt solar water heating systems and do away with electric water heating systems or fossil fuel powered heating systems acquire hence their widespread application in residential homes.
Lastly, there is the need to optimize heat return against pumping costs. Design of houses is changing with many people embracing storied houses due to space limitations. It is common to find many apartments; hence, water must be pumped to the highest point of the building, preferably the rooftop from where it can flow to every room with ease (Mateus and Armando 951). The cost of pumping water to heating systems which are on the roof of a house increased the costs of heating water. Water pumps are expensive to acquire, and since they rely on electric power, they increase the value of operating them. This project seeks to establish ways of lowering or optimizing heat return against pumping costs.
Research and Information about the Location of the Project
England experiences four climatic conditions in a year. The seasons are spring, summer, autumn, and winter. Spring starts from March to May, summer from June to August, autumn from September to November, and winter from December to February (Tzivanidis et al. 88). Temperature and amount of rainfall varies across the year in the city of London, where the project is located. London is a fast expanding city accommodating millions of people. Weather conditions are greatly influenced by the Atlantic Ocean (Bellos et al. 307). Temperature and humidity levels also vary during winter and summer. Weather conditions vary a lot with constant changes from day to day and even sometimes during the day.
Weather conditions in London are sufficient for solar water heating, although sometimes, especially during winter and autumn when conditions are not very ideal for solar water heating. Autumn and winter are mostly cold, windy with a lot of rainfall (Esen 16). The sun rarely shows up in enough time that can take aloe effective solar water heating. However, with an improved water heating system, solar energy can be relied on to slightly heat the water with the aid of electrical power and the temperature maintained at higher levels. Spring is the sunniest season with temperatures rising to about 54 degrees Fahrenheit. Summer is also cool presenting perfect conditions for heating water using solar energy. During summer, the temperature conditions rise to about 60 Fahrenheit (Tzivanidis et al. 89). The duration of sunlight in a day is also extended during summer. With the existing weather conditions, solar water heating systems can work pretty well and reduce the over reliance on electric power of fossil fuel to heat water.
System Research: Types of Solar Hot Water Systems and Types of Collectors
Millions of houses in the United Kingdom are fitted with various types of heating systems. Despite the variation in the configuration of the heating system, the technology used is related and very simple (Zhai, Yang and Wang 1702). Solar water heating systems work by allowing sun rays to strike water, eventually raising the temperature of the water. Sun rays do not directly heat the water. The systems have mechanisms that collect the sun rays before allowing them to heat the water contained in the system. After the water is heated to the desired temperature, it is allowed to flow into a storage tank specifically built not to let the temperature of the water to decrease. Roof mounted solar heaters are the most common in residential houses in London. In some heating systems, a heat transfer fluid traps energy from sunlight before it is allowed to release the heat into the water. In other heating systems, actual portable water is allowed to flow through a tubing system of the heating system and in the process of absorbing energy from the sun (Buker and Saffa 399). The tubes carrying the cool water are fitted close to an absorber to increase the efficiency of the system. In case a separate fluid is used to heat the water, the heating systems must have a heat exchanger to allow the transfer of heat from the liquid to the water. Solar water heating systems have proved to be reliable where they are carefully designed to match the prevailing weather conditions and the amount of water to heat within a given period to meet the demand for the heated water. Therefore, the design of a water heating system should take into account the climatic conditions of the areas will be installed and the amount of load expected.
There exist different types of solar water heaters. In the United Kingdom is it common to five types of solar water heating systems in use. The first type of solar water heating system is called the thermosiphon system. Thermosiphon system heats the water or antifreeze fluid. The common antifreeze liquid commonly used in the United Kingdom is the glycol (Mateus and Armando 953). The heated fluid then rises in a pipe through a natural capillarity process, thus moving from the collector tank to the storage reservoir placed at a high altitude to the collection tank. The system does not require any pumping mechanism, and therefore, no electricity is required. In such a water heating system, water absorbs heat as it more through the ducts until a given temperature is achieved. The system also works on the principle that hot water is less dense, hence rises on top of cold water (Esen 18). Thermosiphon system works well in areas with high sunshine intensity over long hours. The storage tanks are insulated with a nonconductor to minimize loss of heat through surface effect.
Direct circulation systems are another type of solar water heating system. In this configuration, water is pumped from the storage tank to the collector tanks when sun rays are striking the system. The system is protected from freezing or having ice drops in the system by recirculating hot water from the storage tanks or flushing the collector with preheated water (Buker and Saffa 403). Recirculating preheated water increases the efficiency of the system and lowers the amount of time required for the system to heat water once the water is incorporated into the system. The methods are used in tropical areas where the temperature rarely falls to freezing point.
Another type of solar water heating systems is called a drain down system, which is an indirect water heating system. The system uses a heat exchanger to heat water by allowing the transfer of heat from the heated liquid to the water (Kylili et al. 103). During cold seasons or when the sun rays are not available for an extended period the collector fluid is drained from the system, so that is it does not freeze. Drain down system is related to another type of solar heaters known as indirect water heating systems whereby a freeze protected liquid is allowed to pass through a closed loop, allowing heat to move into the water to be heated through a heat exchanger. Indirect water heating systems have a heating efficiency of eighty to ninety percent (Jamar et al. 182). Water-ethylene glycol solution is the most prevalently used to prevent freezing of any liquid that remains in the system after the operation.
The last type of solar water heating systems is called an air system. In this type of heating system, collectors warms the air which is then moved with the aid of a fan through the air to the water heat exchanger. Water flowing into the heat exchanger extract heat from the warmed up air thus, coming out when hot (Qu, Hongxi and David 174). Air systems are not very efficient, hence not widely used in domestic and industrial heating. Direct circulation, thermosiphon, or system that are activated by water pumps require high maintenance cost despite the high installation costs; hence, they are not very popular. Indirect heating systems and air systems are mostly in use due to the least resources required to maintain them after installation. Air system is not very efficient, but desirable where there is a need to keep the cost of maintaining the water heating system as low as possible.
Heat Collectors
There are three types of solar hot water systems; flat plate collector, evacuated tube collector, and systems with a heat pump. A flat plate collector and evacuated tube collector used as a collecting system placed on the roof where the solar heaters are located to receive direct sunlight. The collectors absorb the sun rays which are heated and transfer the heat to the water being heated (Shirazi et al. 959). The water to the heated is pumped through the collectors, thus raising their temperatures. The water heats up as the sun hits the collectors. When the sun’s intensity is low, the system cannot heat water unless it has a backup system that allows alternative sources of energy to be used to heat the water. To ensure availability of hot water even when the sun is not shining, the systems are built with an insulated water tank where hot water is stored for use even at night when the sun is not shining hence the system cannot be relied on to supply hot water.
Heat pump systems use a different type of solar power. Unlike the conventional solar heating system that uses sun rays to heat water directly, heat pump systems used air from the atmosphere to heat water (Bellos et al. 305). Air is sucked into the system using a heat pumped. The air having more energy than water is allowed to pass through water, thus increasing the temperature of the water. Even in winter, the air always has enough energy to heat water to a boiling point. Heat pumps used to circulate air from the environment into the system an out do not use electric power. The heat pumps are air conditioners in heating mode.
Concept: Design Requirement
Water heating systems have intricate designs and equipment, something that affected their use in residential houses. This project seeks to design a simple water heating system that will be simple to install and operate. Many people who do not have profound knowledge and skills required to install a complex water heating system successfully. People find it hard to interpret installation manuals due to limited technological information available to them. The convenience of using fossil fuel or electrical systems to heat water has made them the favorite among many people. This project wishes to design a simple system that any layperson can install and operate. The project will use cheap materials that are easily accessible to design and build an efficient solar-powered water heating system. The waster system will be able to provide enough heated water for domestic use. The design has considered the need to have approximately a hundred liters of water per day. Another design requirement deliberated in this report is the need to optimize heat return against pumping cost. Pumping costs have been blamed for increasing the cost of water heating, making water heaters less accessible. It is irrational to spend resources on installing and maintaining a solar water heater while paying higher costs to pump water into the system for heating. This design, therefore, considers the need to have a system that will significantly cut cost associated with pumping water into the system for heating.
Design Criteria Physical Modeling of Thermo-Siphon Effects in Pump Free Flows
Thermosiphon solar water heaters rely on the energy from the sun to heat water. The amount of water the system can heat over a given period depends on the physical size of the water heating system, the intensity of the sun, the demand for heated water and the temperature of the initial water to the final temperature the water should be and materials used to create the system. The system operates on the principle of buoyancy, whereby density variation between warmer and colder liquid varies (Buker and Saffa 406). The difference in density creates an imbalance that allows the fluid to flow from one container to another with the aid of the gravitational force. Water is thus able to circulate naturally and get heated in the collector before it moves to the storage tank. The systems have several components, each performing specific functions. A typical thermal siphon system has solar collector, storage tank, connecting pumps, heat exchangers, and a check valve that inhibits backflow of the water in the system.
The Development of composite polymer materials has enabled the use of certain polymer materials in the construction of a water heater at cheaper costs without compromising on the efficiency of the systems (Tzivanidis et al. 903). The collector should be affordable, light in weight, and non corrosive. The external material of the collector is made from ultraviolet stabilized polyethylene. Suing polymer materials to make the absorber plate, pipes, cover, and collector cae can make the whole system be half the weight of a similar system made from a metallic material. Lighter equipment is more comfortable to install hence fabricating the equipment using the polymer material will lead to the attainment of one of the goals of the system to make it easy to install.
The absorber plate is made up of one sheet or more of small rectangular shaped layers. The absorber plate is made from material with a high thermal conductivity index such as copper, aluminum, stainless steel, galvanized steel, mild steel or certain types of polymers. The absorber is then painted black to attract the sun rays striking the equipment (Zhai, Yang and Wang 1704). The transparent cover is used to protect the absorber plate from harsh weather conditions and reduce convective heat transfer from the top. The transparent cover creates a greenhouse effect within the system by allowing incident solar radiation into the system while preventing reflected rays from the absorber. The cover is relatively opaque; hence, outgoing longwave radiation rays cannot pass through.
The insulation material is placed on the sides and back and sides of the collector to reduce heat losses. The insulating material should be able to conduct heat out of the system. Conventional insulation materials include mineral fiber, glass fiber, glass wools, and polyurethane foam (Mateus and Armando 953). The seals protect the heating system collector from weather conditions. The casing also prevents the system from mechanical damage.
The storage tank stores heated water on the upper side of the system. Connecting pipes are another component of the system and are divided into two. First, there are the down comer systems that connect the bottom part of the system with the inlet at the tip of the collector. Secondly, the up riser connecting pipes link the outlet of the collector with the inlet to the storage tank (Qu, Hongxi and David 169). Connecting pipes are well insulated to prevent loss of heat as water flows through the pipes.
Design Description and Analysis
The solar-powered heating systems design will be whereby the fin, tube, and serpentine and and which are interconnected to achieve the heating process. The flat solar heater collector will be arranged in parallel to each other. The parallel arranged tubes in the solar collector are referred to as riser while the two perpendicular horizontal tubes are named headers (Freeman, Klaus and Christos 609). The diameters of the risers and the space between the risers have an impact on the efficiency of the heating system hence, are carefully designed. Other factors that influence the effectiveness of the heating system apart from the tube spacing are the tube center to center distance, number of risers making up the system and the inclination of the collection about the sun.
Sun rays striking the system can be reflected if the spacing between the absorbers and the cover plate is now well determined. To reduce the amount of heat loosed from the absorber plate, one or several transparent covers are put at a certain height above the absorber plate (Esen 15). The flow of water to be heated through the risers is almost equal in all risers in the systems. However, in a thermosiphon systems flow in the first two risers vary from the flow in other risers. Moreover, flow in a thermosiphon system is relatively small compared to systems that use pumps to circulate water through the system.
The storage tanks store the heated water at relatively stable temperature; hence, it has to be well insulated to prevent loss of energy gained by the heated water. The size of the storage tanks should be related to the size of the collector (Buker and Saffa 406). Smaller storage tanks are desired due to lower surface areas that limit the loss of energy through surface effect.
During winter, the solar-powered heating system does not perform as required due to lack of enough sunlight or required intensity. Therefore, it is becoming typical for solar-powered water heating systems to have auxiliary heater powers which enable the use of the equipment, even in case of insufficient solar energy (Bellos et al. 312). Supplemental heating allows the system to meet the demand for hot water in all weather conditions. There are two possible arrangements for the auxiliary heating system; the configurations are the in-tank supplemental source of energy, where the setup uses either electricity for heating coil from a boiler with the arrangement being integrated into the tank and the most prevalent design of the auxiliary heating system, and the external supplemental source of energy whereby the auxiliary heater does not form part of the heating loop of the solar system (Qu, Hongxi and David 173). External auxiliary design is usually fitted between the outlet and the solar-powered water heating system and where the heated water will be used.
Reverse flow can be experienced in a thermosiphon flow in case of poor design and configuration of the pipes supplying water around the collector. The rate of flow of water in the system affects the performance of the solar-powered heating systems; hence, it should be well determined to ensure optimum performance of the system. Inappropriate determination and design of flow rate affects the performance of the system and can affect its working. Water to be heated can circulate independently through the system due to temperature difference. The rate of flow of water in the system varies based on the intensity of the sun (Zhai, Yang and Wang 1704). Flow in the systems in many cases is assumed to be quasi-steady. Changes in the amount of solar intensity heating the collector affect the heating, hence the flow of water in the system. Therefore, it is challenging to maintain a steady flow in the system.
How to Reduce the Cost of Installation
The project will minimize installation costs by using materials that are cheap to acquire and a design that is easy to install. The composite material used that are affordable, unlike expensive metallic materials. Similar products existing in the market are made from metallic materials which makes the whole product expensive. Furthermore, installing metallic components on rooftops requires specialized fasteners which are costly to acquire. This project will use composite materials that allow the use of adhesives to install the equipment. Use of standard size products will ensure secure fixing, and hence the experts will not be required to oversee the installation process. Standardization of the product parts will ensure easy interchangeability of parts in case they break or malfunction, therefore, reducing the cost of acquiring and installing the products. Users will be provided with a guidebook on how to install the heater and carry out any repair activity.
Optimize Heat Return Against Pumping Costs
The use of composite materials with poor thermal conductivity will optimize heat return against pumping costs. These materials are poor conductors of heat, hence will not allow the decrease in temperature of water once it is heated. Composite materials are selected for use in the production of the equipment due to their relatively stable condition even when the water is too cold or even at boiling point. Secondly, the length over which heated water will have to move will be shortened. The distance from the collector to the storage tanks will have to be as low as possible to ensure the minimum time it took in moving the water from one point to another. Secondly, the duct carrying heated water will be well insulated to prevent any heat loss through surface effect. The design will ensure the surface area to volume ratio is as small as possible.
Conclusions
The decision to design a solar-powered water heating system reflects the importance of the systems in reducing the over reliance on electric power and fossil fuel in heating water, especially for domestic uses. There is increased interest in using systems that rely on green energy due to their benefits and ability to contribute to environmental conservation. Solar powered systems have been established to be critical in cutting the cost of electricity. The storage tank also determines the efficiency of the system. The storage tank should also well insulated to prevent loss of heat through surface effect. The quality of materials making the collector should also be able to absorb as much energy as possible to be able to heat water in the systems efficiently.
Recommendations
Solar powered water heating systems increase the comfort of dwellings and also by cutting the cost of energy consumed. Houses in the United Kingdom can be fitted with an efficient solar-powered water heating system to reduce the over reliance on electricity or fossil fuel for water heating. Future studies should focus on how solar powered solar heating systems can be installed and shared among several people living in the same apartments. One extensive solar-powered water heating system can be designed for an entire apartment, and the water heated distributed to everyone living within the residence. Future studies should also explore how the systems can be integrated into building designs to ensure all houses have solar power heating systems.
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