« Will Higher Heat Content in Trash Help Waste-to-Energy Stocks? | Main | Energy Storage: Q4 2012 Winners and Losers »


       

Geothermal Transmission 101

Paul Schwabe

Among renewable resources, one of the most valuable attributes of geothermal electricity is the baseload characteristic of the energy resource. That is, geothermal electricity generators are able to deliver a stable level of power production over time. Yet for better or worse, this baseload characteristic—along with other notable factors such as size constraints and varying market segments—reveals that interconnecting a geothermal plant to a transmission or distribution system poses unique challenges compared to other renewable energy technologies [1].

A recent report by NREL, "Geothermal Power and Interconnection: The Economics of Getting to the Market," delves into the specialized world of geothermal transmission. Among other things, this report finds that from a transmission perspective, not all types of geothermal energy technologies are treated equally. Conventional hydrothermal technologies likely fit differently into the transmission framework than do emerging geothermal technologies such as enhanced geothermal systems (EGS), co-produced geothermal with oil and gas facilities and geopressured geothermal.

Table 1 shows three geothermal technologies and the corresponding market segment they serve. It also describes how particular attributes of each technology present challenges to connecting to the grid and how they may be considered in long term system planning.

For example, due to their large project size and their proven commercial viability, hydrothermal geothermal technologies offer a wide range of transmission options; the electricity produced by the plants can serve either local grid networks or be exported to other networks (referred to as balancing authorities, "BA," in Table 1). The report's author suggests that until they are proven, emerging technologies such as EGS are best utilized serving their home network, but if successful, electricity from these new technologies could eventually be transmitted to other networks as well. Meanwhile, co-produced and geopressured geothermal are likely restricted to distributed generation applications due to remote project locations, large electrical demand of the oil or gas facilities, and relatively small generation capacities (i.e., less than 5 MW).


Table showing the attributes, challenges and
long term system planning characteristics for conventional
hydrothermal geothermal, co-production geothermal, and
emerging technologies. Table describes each of these
categories for distributed generation, local network
generation, power sales to another balancing authority
using existing lines and power sales to another balancing
authority using new lines.

Table 1. Geothermal Generation Groupings and Transmission Requirements. Source: [1]

The author also finds that there are several emerging markets in the Western United States where there is expected to be a near-term need for new baseload generation. These markets are largely where coal plants are expected to be taken offline in the next 5-10 years.  It is estimated that there will be more than 3,000 MW of new baseload opportunities that will emerge from diminished coal usage across the Western United States [1].  While some of these resources will be replaced with other forms of fossil fuel electricity generation such as natural gas, there is likely enough of a need to also elicit interest from geothermal developers.

The report also shows what the author succinctly describes as "The Uphill Economics of New Transmission." Generally, the cost of new transmission is determined by how much electricity the new line caries. Due to economies of scale, a MW of carrying capability on a large transmission line is cheaper than a MW of carrying capability on a smaller line.  Figure 1 shows the cost of transmission per megawatt served over various transmission line sizes.


Bar chart showing the Dollar per MW capacity of
new electricity transmission. The cost per MW is shown for
both 100 mile and 600 mile lines and at different voltage
levels. The cost per MW generally decrease and the line
capacities’ increase.

Figure 1. Total Line and Substation Costs per Megawatt of Transmission Capability.  Source: [1]

Given that most U.S. geothermal plants are less than 80 megawatts in capacity, they are relatively small energy generators compared to other baseload electricity sources such as coal or natural gas power plants.  Without economies of scale, new transmission for commercially available hydrothermal geothermal is a significant challenge, and in practice, drives even proven hydrothermal geothermal development into areas with existing, but underutilized transmission in place [1].

As each of these geothermal technologies offers the benefit of a stable electricity generation profile, there is likely to be a demand for the energy they produce. However, the role geothermal energy will play in long term transmission planning remains to be seen.

Paul Schwabe is an Energy Analyst with the National Renewable Energy Laboratory’s project finance team and has significant expertise in wind and geothermal projects. He has over 10 years of experience in the energy industry, including electricity market analysis, natural gas forecasting, and financial modeling.
This article was first published on the Renewable Energy Project Finance blog.



was posted on AltEnergyStocks.com.


       

advertise here


Oil and Gas





Post a comment

(If you haven't left a comment here before, you may need to be approved by the site owner before your comment will appear. Until then, it won't appear on the entry. Thanks for waiting.)

Featured Companies











Oil and Gas


Search This Site


Subscribe to this Blog

Enter your email address:

Delivered by FeedBurner


Subscribe by RSS Feed



Twitter Headlines

Certifications and Site Mentions


New York Times

Wall Street Journal





USA Today

Forbes

The Scientist

USA Today

Seeking Alpha Certified

Twitter Updates