Advances in Solar Heating and Cooling

Ruzhu Wang, Tianshu Ge

• Publisher: Woodhead Publishing
• Year: 2016
• Print ISBN: 9780081003015
• eBook ISBN: 9780081003022
• Topic: Technology & Engineering
• Subtopic: Renewable Power Resources
• Index: Technology & Engineering

Advances in Solar Heating and Cooling presents new information on the growing concerns about climate change, the security of energy supplies, and the ongoing interest in replacing fossil fuels with renewable energy sources. The amount of energy used for heating and cooling is very significant, estimated, for example, as half of final energy consumption in Europe. Solar thermal installations have the potential to meet a large proportion of the heating and cooling needs of both buildings and industry and the number of solar thermal installations is increasing rapidly. This book provides an authoritative review of the latest research in solar heating and cooling technologies and applications. - Provides researchers in academia and industry with an authoritative overview of heating and cooling for buildings and industry in one convenient volume - Part III, 'Solar cooling technologies' is contributed by authors from Shanghai Jiao Tong University, which is a world-leader in this area - Covers advanced applications from zero-energy buildings, through industrial process heat to district heating and cooling

Part One

Introduction

Outline

1. Introduction to solar heating and cooling systems

2. Resource assessment and site selection for solar heating and cooling systems

3. Energy efficiency and environmental impact of solar heating and cooling systems

1

Introduction to solar heating and cooling systems

R.Z. Wang, Z.Y. Xu, and T.S. Ge Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai, China

Abstract

The solar heating and cooling systems are among the best solutions for the current energy and environment issues. In this chapter, the background and overview of the solar heating and cooling systems are given. In these systems, the energy sources are the solar power, and the consuming components include the heating and cooling devices. In order to ensure the steady operation of solar driven systems, the heat storage systems are also necessary. In this case, the different choices of solar energy, solar heating, solar cooling and heat storage are briefly introduced in this chapter. A technology roadmap is given at last which provides a clear connection between these introduced technologies.

Keywords

Heat storage; Roadmap; Solar cooling; Solar heating

1.1. Background

Energy and environment are two vital issues for modern society. Fossil fuels including coal, oil, and natural gas are nonrenewable and cannot provide sufficient energy sources for eternal time. In addition, utilization of these traditional energy resources has caused severe environmental problems, including global warming, air pollution, and so on. Global warming is mainly caused by carbon dioxide (CO₂) emissions, which raises the global average temperature and sea level. To solve these problems, several negotiations and conferences have been held, such as the United Nations Framework Convention on Climate Change negotiated in 1992, in which many countries participated. Conferences of the Parties have been held many times in Kyoto, Bali, Copenhagen, and Paris, in which greenhouse gas emission reduction was proposed as an important task in the world. It can be seen that to build a sustainable and green future, both energy resources and the energy-consuming systems should be reconsidered under the modern energy background.

For the energy resources, renewable energy resources including solar energy, wind power, and hydropower are among the best choices. Compared with traditional energy resources, renewable energy resources are abundant and environmentally friendly. Among the different renewable energy resources, solar energy is one of the most attractive options. It is a clean and endless power with wide distribution. In this case, there are numerous researches and businesses about solar energy and solar driven systems.

For energy-consuming systems, the heating and cooling systems take a big proportion of the entire society energy consumption. It could be as high as 30% of the total energy consumption for those developed countries. If China is taken for an example, then the energy consumption for buildings (heating, cooling, hot water supply, lighting, etc.) is greater than 10% of the total energy used. Green and energy-saving heating and cooling systems should be developed.

Considering the merits of renewable energy and high energy consumption of heating/cooling systems, the adoption of a solar energy-driven system to fulfill the heating and cooling demand is a promising solution for the aforementioned problems. Researchers all over the world have conducted innovative studies in this area. To provide a general guideline and roadmap of the solar heating and cooling systems, related technologies, including solar power, solar heating, solar cooling, solar thermal storage, and some advanced systems, will be introduced in this book.

1.2. Overview of solar heating and cooling systems

Solar energy is the primary light and heat resource of the Earth. It can provide eternal energy to maintain the atmosphere temperature and germinate plants. With technological developments, solar energy can be utilized more and more efficiently and economically.

In a solar heating and cooling system, solar energy has the potential to meet a large proportion of the heating and cooling needs of buildings and industry. There are also numerous technologies for different heat source temperatures and specific demands. To ensure steady and long-term solar utilization, heat storage is also essential. In this chapter, an overview of the solar heating and cooling technologies, including solar energy, solar heating, solar cooling, and heat storage, will be given.

1.2.1. Solar energy

Solar energy is the energy source of solar heating and cooling systems. There are mainly two modern ways to collect solar energy. One is to directly adopt the thermal energy produced by solar radiation with use of a solar collector. The solar heat gained could be then transferred to solar heating or cooling applications; this kind of system is also called a solar thermal system. The other one is to transfer solar radiation into electrical power through photovoltaic (PV) material; this kind of system is also called the solar PV system.

When solar energy is integrated with the heating and cooling systems, there are many more options for thermal-driven systems than for electrical-driven systems. In this case, the solar thermal collectors are emphasized and thermal-driven systems have been extensively researched and developed. Because of the significant price reduction of solar photovoltaics in the last 5 years, solar PV-powered systems are also becoming attractive.

There are different classifications of the solar collector. It can be classified into nonconcentrating types and concentrating types. It can also be classified into low-temperature collectors, medium-temperature collectors, and high-temperature collectors according to the working temperature. Low-, medium-, and high-temperature collectors work under 100°C, 100–200°C, and higher than 200°C, respectively. In this chapter, solar collectors are classified into nontracking solar collectors and tracking solar collectors. A brief introduction of solar PV technology is also given.

1.2.1.1. Nontracking solar collectors

This type of solar collector mainly includes the flat-plate collector (FPC), the evacuated-tube collector (ETC), and the compound parabolic concentrator (CPC). They usually work as low- and medium-temperature collectors that are suitable for space-heating and space-cooling. Water, air, or oil can be used as a thermal transport medium.

FPCs: The FPCs usually contain the glazing, absorber plate, heat transfer component, and insulation layer. FPCs are typically used for space-heating or hot water supply. It has low working temperature, but it is simple, cost-effective, and has a long lifetime. It is also easily integrated in buildings.

ETCs: When the climate is not so warm or the working temperature is high, the FPC cannot work efficiently because of heat losses, and the ETCs can be used. In the ETC, the absorber surface with selective coating (absorptivity 95%, emissivity <5%) is placed in a double-layer tube with vacuum between two layers. The vacuum surrounding the absorber can greatly reduce the convection and conduction heat losses. In this case, the efficiency can be increased.

CPCs: To increase the solar collector efficiency, concentrating collectors such as CPCs can be used. The CPC is a nonimaging concentrator with a low concentration ratio. The CPC uses a compound parabolic reflective surface to reflect and concentrate the solar radiation to the focal line. A tubu...

Table of contents

• Cover image
• Title page
• Table of Contents
• Related titles
• Copyright
• List of contributors
• Woodhead Publishing Series in Energy
• Part One. Introduction
• Part Two. Solar heating systems
• Part Three. Solar cooling technologies
• Part Four. Heat storage for solar heating and coolingapplications
• Part Five. Advanced applications of solar heatingand cooling systems
• Index