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Geothermal Heating Systems: How Do They Work?

Schmidt Associates has received an increasing number of inquiries about geothermal heating systems. We are also designing geothermal systems for a variety of projects. This blogs explains that technology.

A geothermal ground source heat pump (GSHP) is an electrically powered system that taps the stored energy of the greatest solar collector in existence: the earth. GSHP systems use the earth’s relatively constant temperature to provide heating, cooling, and hot water for homes and commercial buildings.

spaceatmosphereearth

 

The heat pump system uses solar energy stored in the earth’s crust. Energy is transferred to and from the earth’s surface by solar radiation, wind, and rainfall. At depths greater than 30’, the earth’s temperature remains constant, and is comparable to annual average air temperature.

Between the surface and a depth of 8’ (the maximum depth to install a GSHP horizontal loop of pipes to collect and disperse heat) the ground temperature will swing above and below the annual average air temperature, depending on the geographic location, soil type, and moisture levels. Because of its own insulation, soil temperature is more moderate year round than outside air.

Look for our future blog to learn about four types of geothermal systems.

What is an Energy Model?

Engineers always promise to create an energy model for each project — but what do they mean and why should you care?

Energy Model Diagram BAWhat should you expect at each phase? Like the rest of the facility design, energy modeling grows in detail and complexity at each stage of project development.

Design Performance Modeling during concept and schematic design evaluates:
•  Wall-to-window ratios (how do we balance light vs. energy efficiency?)
•  Effective shading elements
•  Building positioning on the site for maximum energy efficiency

Building Energy Modeling during design development and conceptual design evaluates:
•  Mechanical system effectiveness and differentiators
•  Zoning variables
•  Potential energy costs

Building Operation Modeling during post construction and operation evaluates:
•  Building performance verification
•  Opportunities for optimization

Integrating the right level of energy modeling at each stage in the process ensures that your building is designed and built to save both energy and money. It’s well worth the up-front investment for long-term savings!

Fourth in the Series: How to Balance Your Geothermal Design with Your Building Load

The demand for heating, cooling and hot water—what architects and engineers call “building load”—is constantly changing.

Note that balancing building loads is very different if you are designing a hospital versus an office building, school, or condominium.  But even buildings used 24 hours a day, seven days a week, have fluctuations in demand for heating and cooling.

At night, most office buildings and schools are unoccupied; lights and electrical equipment are shut off.  For all buildings, there are no solar gains at night, the outdoor temperature is lower and ventilation rates are usually reduced.

During the day, outdoor air temperatures increase, people occupy the building, the mass of the building increases in temperature and solar gains shift from one side of the building to the other from morning to afternoon. Cooling loads typically increase and heating loads are further reduced.

To optimize the design of a geothermal system and its geothermal heat exchanger (GHX), the system designer must work in an integrated design process with the Owner, architect, and other members of the design team to balance the loads.

An energy model is used to determine the impact of changes to the building or building systems and the impact of the changes to the GHX.

How do you know if your geothermal system balances building loads?  A well designed system is just the right size and type to handle the hottest days and coolest nights, and it is able to compensate for the variations in the energy model projects.  A well designed geothermal system will produce maximum energy (and money!) savings, and it will keep your operations running smoothly and your occupants comfortable.

Second in the Series: What are the Different Types of Geothermal Heat Pumps?

Eagle Creek Earth Discovery Center Open-Loop System

Eagle Creek Earth Discovery Center
Open-Loop System

Ground source heat pumps (GSHP) can be classified into four basic types.  Choosing the right one depends on the available land area and the soil and rock type at the installation site. The design team will analyze these factors to determine the most economical choice for installing the ground loop.

Closed-Loop Systems
In closed-loop systems, a water or antifreeze solution is circulated through plastic pipes buried beneath the earth’s surface. During the winter, the fluid collects heat from the earth and carries it through the system and into the building. During the summer, the system reverses itself to cool the building by pulling heat from the building, carrying it through the system, and transferring it to the ground.

Pond/Loop Closed-Loop Piping Systems
If a large river or moderate- size pond or lake is available, a closed-loop system can be submerged in it. Some commercial and institutional buildings have artificial ponds for aesthetic or drainage reasons; these may have adequate surface area and depth to fully immerse a closed loop heat exchanger.

Open-Loop Systems
The open-loop portion of a ground-sourced heat pump system is a long plastic pipe buried below the earth’s surface. This plastic pipe allows heat transfer between fluid in the pipe and the earth. The heat pump transfers thermal energy to and from the open buried pipe, a water-sourced heat pump, and an energy distribution system.

Hybrid Geothermal Heat Pump System
A hybrid geothermal heat pump (GHP) can be a lower cost alternative. In hybrid GHPs the ground heat exchanger size is reduced, and an auxiliary heat rejecter (cooling tower) handles the excess heat rejection loads during building cooling operation. The amount of size reduction for the ground heat exchanger in a hybrid system will vary with location and climate, but it must be large enough to handle the building’s heating requirements.

Look for our next blog in this series to learn about the critical steps in geothermal system design.

First in the Series: How does a geothermal heat pump work?

With a growing trend toward sustainability, Schmidt Associates has received an increasing number of inquiries about geothermal heating systems. We are also designing geothermal systems for a variety of projects. This is the first in a series explaining the technology.

A geothermal ground source heat pump (GSHP) is an electrically powered system that taps the stored energy of the greatest solar collector in existence: the earth. GSHP systems use the earth’s relatively constant temperature to provide heating, cooling, and hot water for homes and commercial buildings.

What is geothermal model reduced file

The heat pump system uses solar energy stored in the earth’s crust. Energy is transferred to and from the earth’s surface by solar radiation, wind, and rainfall. At depths greater than 30’, the earth’s temperature remains constant, and is comparable to annual average air temperature.water source heat pump

Between the surface and a depth of 8’ (the maximum depth to install a GSHP horizontal loop of pipes to collect and disperse heat) the ground temperature will swing above and below the annual average air temperature, depending on the geographic location, soil type, and moisture levels. Because of its own insulation, soil temperature is more moderate year round than outside air.

Look for our next blog to learn about four types of geothermal systems.