MEGS Definition

What is MEGS?

A Geothermal System (GS) is a system of fluids, mechanical equipment and electrical control devices that produce energy from heat collected deep in the Earth.  Many of these components are similar to those used to generate electricity in the coal plants that are in use at the present time.  A GS facility would differ from a coal plant in that the heat that is needed is brought by a heat transfer fluid delivered by a pipe system from deep in the Earth, not from burning coal, oil or natural gas.

In much of the United States at a depth one to three miles below the surface are rock layers, called hot rocks, that are at high temperatures (150 to 400 F).  These hot rocks often have low heat transfer rates so that the heat reservoir can be exhausted as heat is extracted in the area near the pipe system.  Enhanced Geothermal Systems (EGS) employ techniques that enhance the flow of heat through the hot rocks to the pipe system, and thus make long term use of individual wells viable.

To replace existing and planned coal plants possibly over a thousand MEGS facilities would be needed in the USA and somewhere near 10,000 in China.  The number would depend on the generation capacity of an average plant.  Each MEGS facility would consist of about a dozen components (See Section 2 for their description).  Mass production techniques would be required to economically produce the large numbers of components needed for these MEGS facilities.  These components would be assembled into Modules that are designed for easy installation and operate at a high efficiency.

MEGS is then, an electric energy generation system that uses Modules of standardized components to bring the heat from deep in the Earth by an Enhanced Geothermal System.  MEGS is Modular Enhanced Geothermal Systems (MEGS).

Section 2 Principles and Components of MEGS

General

MEGS (Modular Enhanced Geothermal Systems) are geothermal systems that can be developed in places (three quarters of the US and in significant parts of other counties) that have temperatures over 160F two miles below the Earth’s surface.  All dimensions and capacities mentioned here are general.  Many of the specifics will be determined as the industry and various study panels work out the details, but understand that in fact, the needed information and technical know-how is well inside the boundaries of current mechanical, electrical, control and chemical engineering knowledge.

Envision a 3-ft diameter two-cavity pipe that runs down two miles to where the temperature of the rock is over 180F.  A heat transfer fluid is pumped down the outside cavity of this pipe and back up a central cavity surrounded by insulation.  The fluid starts down about 55F and returns to the surface at 180F or more.  This is a Geothermal System.

One barrier to extracting heat with a geothermal system is that often the rock strata around the deep end of the pipe transfers heat too slowly. Heat can be taken way faster than it can be replenished from adjoining rock.  There are techniques to enhance the flow of heat through the rock near the deep end of the pipe to insure that the required heat will be available to be transferred up to the surface.  When these enhancing techniques are used, an Enhanced Geothermal System (EGS) is in operation.

The amount of heat available at the surface is a function of four things: 1) the diameter of the pipe, 2) the depth of the well, 3) the speed with which the fluid is pumped and 4) the thermal transfer rate of the rock matrix next to the pipe outside surface at depth.  These four are the source of potential variability in the generation capacity at each site.  To gain manufacturing cost reductions and reliability the Modules at the surface (or rather their components such as heat exchangers, turbines and electric generators) will be mass produced in factories in standard sizes, for example 5MW, 20MW, 80MW or more.  Needed capacity is generated at each site by combined Modules.

The Construction and Deployment of a MEGS Facility

The construction and installation of a MEGS facility will have at least the following steps, and each will require planning and research activity.  These will culminate in a standardized process for future development.

Construction Steps

Step Number  Step Name                 Description

1                   Exploration                Geological Data Gathering

2                   Well Drilling

3                   Enhancement            Choice of Method, Execution

4                   Pipe Insertion            Placing the Pipe in the Well

5                   Surface Equipment     Buildings, Heat Exchange/Turbine, Generator, Pumps

6                   Down Fluid Loading

7                   Testing

8                   Operation

The Technical Components

Each of the following units (and possibly others) of a MEGS implementation will have specific research plans developed.  There will be individual contracts for specific development of many of these units

Devices exist for many of these units and there are a significant number of working production versions.  For example, there are thousands of commercial models of pumps available.  Much of needed development work will be in increasing efficiency in general and making the interactions between subsystems less expensive to build and integrate.  Special attention will need to be paid to advancing the efficiency of heat exchangers.

Table of Components

Unit     Unit Name                         Initial Description

1         Transmission                     Interface to existing Electric Grid

2         Generator                         Conventional generator

3         Turbine                             Turbine Optimized for Fluid 1

4         Heat Exchanger  (HE)         Heat Exchanger Optimized for Fluids 1 & 2

5         Controls                            Integrated Control of all Units

6         Interface – Pump/Pipe/HE   Physical Interface Components

7         Pumps – Fluid 1                 Commercial Pumps

8         Fluid 1                              Turbine Cycle Fluid

9         Pumps – Fluid 2                 Commercial Pumps

10       Fluid 2                              Well Fluid

11       Pipe                                  Chambered steel pipe

12       Bottom Geometry              Bottom end sections of the wall pipe

13       Heat Tras. Rate – Rock       Verified Long Term Heat Transfer Rate

14       Enhancement                    Type and quantities needed for Enhancement

Validating MEGS

Three are several different ways that the concepts that underlie the MEGS way of generating energy must be validated before large numbers of people can be successfully persuaded to provide their time and money to support the implementation phase of MEGS.  They are:

Energy flow

Fluid flow

Mechanical/Software Functionality

Cost

MEGSorg will present definitions and descriptions of the elements of MEGS in ways that are understandable to the general public.  ill be mass produced in factories in standard sizes, for example 5MW, 20 MW, 80MW or more.  Needed capacity is generated at each site by combined Modules.