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Heat Pump Systems

Lee Layton, P.E.


Course Outline

This course begins with a brief introduction to the heat pump market with a review of energy consumption in residential and small commercial applications.  The basic operation of a heat pump is covered including the cooling, heating, and defrost modes.

The various types of heat pumps systems are then reviewed with a focus on the advantages and disadvantages of each type of system.  The performance parameters, such as SEER, EER, COP, that are used to evaluate heat pumps are then reviewed.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

After taking this course you should,

Intended Audience

This course is intended for electrical engineers, mechanical engineers, architects and others who want to understand how an electric heat pump operates.

Benefit to Attendees

Taking this course will give you a better understanding of the electric heat pump market, how a heat pump operates, and the advantages and disadvantages of the various types of heat pumps in use today.

Course Introduction

For climates with moderate heating and cooling needs, heat pumps offer an energy-efficient alternative to furnaces and air conditioners. Like a refrigerator, heat pumps use electricity to move heat from a cool space into a warm space, making the cool space cooler and the warm space warmer. During the heating season, heat pumps move heat from the cool outdoors into a warm house; during the cooling season, heat pumps move heat from a cool house into the warm outdoors. Because they move heat rather than generate heat, heat pumps can provide up to four times the amount of energy they consume.

A heat pump is a device that moves heat from one location to another location using mechanical work. Most heat pump technology moves heat from a low temperature heat ‘source’ to a higher temperature heat ‘sink’. A heat pump for heating and cooling a building is known as a reversible cycle heat pump.  Other examples of heat pumps are food refrigerators, freezers, and air conditioners.  These systems can also operate in reverse, producing heat.

Heat pumps can be thought of as a heat engine which is operating in reverse.  Heat flows naturally from a higher to a lower temperature. Heat pumps, however, are able to force the heat flow in the other direction, using a relatively small amount of drive energy such as electricity. Thus heat pumps can transfer heat from natural heat sources in the surroundings, such as the air, ground or water, or from man-made heat sources such as industrial or domestic waste, to a building or an industrial application. Heat pumps can also be used for cooling. Heat is then transferred in the opposite direction, from the application that is cooled, to surroundings at a higher temperature. Sometimes the excess heat from cooling is used to meet a simultaneous heat demand.

In order to transport heat from a heat source to a heat sink, external energy is needed to drive the heat pump. Theoretically, the total heat delivered by the heat pump is equal to the heat extracted from the heat source, plus the amount of drive energy supplied.

The most common type of heat pump is the air-source heat pump, which transfers heat between the house and the outside air. It works by exploiting the physical properties of an evaporating and condensing fluid known as a refrigerant. In heating, ventilation, and cooling (HVAC) applications, a heat pump normally refers to a vapor-compression refrigeration device that includes a reversing valve and optimized heat exchangers so that the direction of heat flow may be reversed. When heating with electricity, a heat pump can reduce the amount of electricity used for heating by as much as 30%–40%.  High-efficiency heat pumps also dehumidify better than standard central air conditioners, resulting in less energy usage and more cooling comfort in summer months. However, the efficiency of most air-source heat pumps as a heat source drops dramatically at low temperatures, generally making them unsuitable for cold climates, although there are systems that can overcome that problem.

Higher efficiencies are achieved with geothermal (ground-source or water-source) heat pumps, which transfer heat between the residence and the ground or a nearby water source. Although they cost more to install, geothermal heat pumps have low operating costs because they take advantage of relatively constant ground or water temperatures.  Ground-source or water-source heat pumps can be used in more extreme climatic conditions than air-source heat pumps, and customer satisfaction with the systems is very high.

Another type of heat pump for residential systems is the absorption heat pump, also called a gas-fired heat pump. Absorption heat pumps use heat as their energy source, and can be driven with a wide variety of heat sources.

Because heat pumps consume less primary energy than conventional heating systems, they are an important technology for reducing gas emissions that harm the environment, such as carbon dioxide (CO2), sulphur dioxide (SO2) and nitrogen oxides (NOx). However, the overall environmental impact of electric heat pumps depends very much on how the electricity is produced. Heat pumps driven by electricity from, for instance, hydropower or renewable energy reduce emissions more significantly than if the electricity is generated by coal, oil or gas-fired power plants.

Course Content

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Heat Pump Systems

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Course Summary

A heat pump is an energy-efficient alternative to furnaces and air conditioners. Because they move heat rather than generate heat, heat pumps can provide up to four times the amount of energy they consume.  Heat pumps are able to force the heat flow in the other direction, using a relatively small amount of drive energy.  Thus, heat pumps can transfer heat from natural heat sources in the surroundings, such as the air, ground or water, or from man-made heat sources such as industrial or domestic waste, to a building. Heat pumps can also be used for cooling. Heat is then transferred in the opposite direction, from the application that is cooled, to surroundings at a higher temperature.

In this course, we have looked at the basic operation of heat pumps for heating and cooling residential and small commercial buildings.  The components of a heat pump system, the basic operating cycles and the various performance measurements were reviewed. 

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.