The phase one portion of the study included narrowing down areas with renewable resources to the zones where the best resources in each state were available. This includes areas of high solar irradiation and sufficient wind speeds at 50 meters above ground. The WECC (Western Energy Coordination Council) peak load was 150GW in 2007, so the resulting 180GW of generation capability identified by the study could significantly mitigate peak load.

Other factors that were included in the study were sufficient density – enough to provide 1,500MW of energy in a 100 mile radius, which would justify a 500kV transmission line from the zone to the demand region. Also excluded were protected areas identified by the BLM and other federal government agencies where the development of renewables is prohibited, not congruent with the development intent or could impact sensitive environmental conditions. Also not included were smaller renewable installations – generally at the local level like PV panels on rooftops.

After all is said and done, the 11 western states identified 80GW of solar thermal, about 74GW of wind, 2.5GW of biomass and 29GW of geothermal, for a total of 185GW (though only about 162GW of that was in WREZ areas).

The 11 western states in the lower 48 in 2007 consumed 667,670 GWh. In the same states, the renewable zones identified could possibly contribute over 442,000, or 66% of the total power consumption. Some states like Montana, Wyoming, New Mexico and Nevada could export renewable energy to states that wouldn’t be able to produce anywhere near what they consume – California.

Future phases of this study will analyse and create a transmission plan, as well as developing a regional purchasing system for utilities to meet their states’ RPS (renewable portfolio standards) goals, and finally getting the various local, state and federal jurisdictions to work together harmoniously in the permitting and construction process to get renewables from generation to distribution.

Solar PV is often looked to as a simple solution – put the panels on your roof and you can generate between 50 and 100% of your power requirements over the year. It simplifies a number of things – like treating the grid like a gigantic battery, where energy generated that isn’t used locally is sent out to the grid and when the panels aren’t producing enough, to pull off the grid to make up the difference. The issue is that if you have a large PV installation designed to generate power, and the sun goes behind a cloud and your output drops by 50%, the power demand doesn’t instantly drop by that much, so you have to make it up elsewhere. This “elsewhere” is usually natural gas, but natural gas can only spin up so fast – from 50% to 90% in 6-7 minutes, by then the sun might be back out from the cloud and production rates are already returned to normal. This limits the amount of large free field PV that can be installed – its not so much about cloudy and rainy days since you can forecast and plan for additional resources to be run that day, its the intermittent cloudy days where your output varies all day. Geographically distributing the generation can help but building large facilities far away from each other can hurt the total cost effectiveness of the project. I would put the overall piece of the generation pie at 2.5% of total energy generation.

The proliferation of roof-top systems could double these numbers if utilities can get a better grip on the demand side – being able to turn off non-essential grid demands like plug-in cars, and being able to ramp power quicker when PV generation quickly drops (draw on energy storage – either batteries, thermal or kinetic). This is where the smart grid is absolutely critical. Also, predictive systems could also cut consumption – your air conditioning unit sees that the sun is behind a cloud so it can reduce energy consumed because your house isn’t exposed to direct sunlight and wont heat up as quickly as it would have otherwise, instead of just turning on when the internal temperature creeps up.

Solar Thermal is an easier approach from the grid operator’s perspective. Since solar thermal is still driven by hot liquids and turbines, it has a higher generational “inertia” than solar PV does, that is to say the output doesn’t change as quickly as PV does when the sun goes behind a cloud. This would allow for other natural gas turbines to speed up and add generation output. Likewise, its possible to build storage in the form of a large molten salt tank that could be drawn on when the sun goes behind a cloud, as well as after the sun sets. A 100MW facility that had 50MWh thermal storage could provide for up to 30 minutes without any sun, or a proportionally longer time during partial sun exposure. Thermal storage is still far preferable than batteries for the foreseeable future. It wont be until there are large quantities of partially used batteries to be recycled for other uses (old PHEV batteries that are retired after 10 years) that battery storage will become more useful. This technology has a substantially larger piece of the pie – 12.5% of total energy generation.

Wind has an upper limited of around 20% with today’s “dumb” grid. With the creation of a smart grid and devices that can defer their energy consumption to cheaper times or whenever there is extra capacity, wind will be able to grow beyond the 20% barrier. Beyond that, other large scale storage mechanisms like pumped hydro would allow for wind energy to be converted into kinetic energy in the form of water stored in a reservoir, however this is a fairly expensive exercise – instead of just the cost of the wind turbine and transmission lines, the additional pump storage system costs have to be factored into the total cost of wind power. Wind could account for about 20% of energy generated.

Geothermal technologies aren’t really limited by reliability, since they substitute for baseload power (coal, nuclear). Rather its limited by the land suitable for geothermal wells, mostly in the western parts of the US. Standard geothermal requires pumping hot water (at least 300° F) from underground and letting it turn into steam to turn turbines and then either releasing the steam into the atmosphere or attempting to recapture it and put it back into the ground. Even lower temperature geothermal, which can use water down to about 165°F, still is limited in areas it can be used, though it provides a larger footprint in terms of how much energy we can extract. Enhanced Geothermal involves fining hot rock and then artificially recharging the aquifer with water to be able to extract that hot water elsewhere and use it for generation purposes. Combined, these technologies would only account for about 5-7% of installed rated power, but because of their high capacity factor provide around 15% of our energy generation portfolio.

Biomass, using waste from humans (trash) as well as marginal plant products (the famous example is  switchgrass) to produce power is also an option, however it is further behind from a technological standpoint that solar or wind. However it could function as a baseload power plant, which is highly desirable from a CO2 reduction standpoint since it can replace coal power. The biomass is gassified and then put through a turbine to generate electricity. I don’t see this ramping up soon, the projects are currently very small and no where the size for what a utility would require for a generation facility (100MW or larger).

Combined, all of these green technologies can account for approximately 50% of our energy generation needs. When combined with nuclear and hydro, we could have 80% of our energy from non-fossil fuel sources. However its not going to be that easy to shut off coal – only geothermal and biomass have sufficiently high enough capacity factors to replace coal. Combined, they’re likely to only be able to displace about 30% of coal’s energy output.

To eliminate coal will require a very large, geographically diverse wind power footprint – with a larger capacity than I think the current grid can support. To replace 70% of coal with wind power, it would take approximately 450GW of installed capacity – higher than most estimates have predicted.

Any final drive to remove the last few coal plants by 2030 will require replacing them with baseload natural gas power plants, which are subject to the volatile prices of natural gas (in 2008, natural gas was $9/MMBTU, now its approximately $3.50/MMBTU, I have no idea where it’ll be next year).

We should always work for a cleaner environment, but ignore the reality of technology at this point is not advisable. Where alternatives exist (geothermal in the west, solar in the southwest, wind in the midwest) we should shun coal power, but we don’t have the option to turn it off completely. Cap and Trade could push us further in that direction, but it shouldn’t have the end goal of eliminating coal, rather seeking to reduce CO2 – which would have the effect of preventing coal power expansion and forcing coal burning facilities to do what they can (including building newer, comparatively cleaner) to clean up.

Raser posted a video of enthusiastic workers turning the switch to start sending power to California. Their technology allows the usage of water down to about 60C, well below the 150-180C water temperatures needed for traditional geothermal power generation.

The technology used is a binary system, where the hot water’s heat is transferred into a working fluid that has a much lower boiling point that water. This will flash boil the liquid and convert it to steam, which will turn the turbine and generate electricity. After the steam has passed through the turbine, it will collect in a second tank where cool water is circulated through which cools the steam and returns it to a liquid. From there it is pushed through a pump and put back into the first tank with the hot water.

This system in its current form can generate about 280kW. This facility, the Hatch Generating Plant, has 50 of these units, which will generate 10 to 11MW of geothermal energy for use in California, where renewable energy portfolio standards (RPS) require 20% of the energy used to be renewable by the end of 2010 and 33% by 2020.

Raser has a commitment from Merril Lynch to provide for project financing up to 155MW. This allows Merril Lynch to take advantage of the 10% investment tax credit for geothermal passed under the stimulus package of 2009. They currently have seven additional projects under development in the United States.

The two plants cost 200 million dollars and will provide 400 million kWh of energy annually, which is enough for 60,000 homes. The 400 million kWh from 65MW is a capacity factor of 70%, which is low from my understanding of geothermal, though its possible its just a conservative estimate.

Capacity factor is one of the most important things to consider when comparing renewable energy sources – solar has an average capacity factor of 25%, and wind is about 30%. This means that over the course of a year, the facility is only outputting power at 30% of its rated capacity, so a 100MW wind farm is on average outputting 30MW at any given time. Geothermal generally has very high capacity factors, between 75-90%, which means that an equivalent solar power system would need to be about 200MW to produce the same 400 million kWh of energy annually.

The problem of course is that geothermal resources are very limited. Nationally, geothermal is really only feasible in the western US, in states like Nevada, Idaho, Wyoming, Utah and Oregon. The total estimated recoverable geothermal-based energy is about 20-25GW in the western US, with “enhanced” geothermal systems (still primarily in the research and development phase, with a few operational plants in production) providing an additional recoverable 80GW of energy. This baseload of roughly 100GW could provide the current (2009) baseload needs for the western United States, eliminating the need for coal, nuclear and natural gas baseload power plants. Natural gas would still be needed for peak loads, but combined with solar PV and thermal we can manage to generate and store that energy for peak load in the winter and summer. This also doesn’t account for the increase in per capita energy consumption, which is where effciency programs like Energy Star come in to play.

Geothermal resources in northern Nevada underscore need for a proposed north/south 500kV line to connect northern geothermal to Las Vegas. and points beyond. It is estimated that there is a total of 2.5-3GW worth of conventional geothermal available in the state, which would account for a significant piece of the baseload energy the state needs. At our current rate, we are building about 100MW per year, with a current installed capacity of roughly 370MW of geothermal resources in-state, we will reach this in about 20 years.

Whats the difference between normal geothermal and enhanced geothermal? Water. In traditional geothermal systems, the system relies on hot water coming out of the ground that was already in the ground. Meanwhile, enhanced geothermal relies on pumping water back into the ground at high pressures over hot, dry rock (which there is more of than hot, wet rock), and reclaiming that heated water through other wells and using that water to transfer that heat into energy.

One of the interesting side effects of the stark decline in the price of oil and the subsequent demand reduction is that the same type of equipment that you need to drill wells for oil is the same equipment you need to drill for geothermal wells. So if the oil company equipment suppliers have been ramping supply for drilling equipment the past few months as prices crossed $90, $100, $125, and up to $147, they’ll now be left with excess inventory after the price per barrel dropped in half. This makes a great time for geothermal companies to acquire the drilling equipment necessary to start drilling due to the dynamics of the oil market.

To get off the ground, companies can start in areas near existing traditional geothermal systems. This would allow for low risk projects – nearby access to roads, powerlines and other necessary equipment will allow them to test a few wells. Most of the land suitable for EGS is concentrated on the western US – states like Nevada, Oregon, Idaho, Utah and Colorado.

In Google’s recent report, they had estimated 80GW of geothermal – 65GW of which was enhanced geothermal. Because of the very high capacity factors however, that 80GW of geothermal outproduced solar and wind in terms of annual GWh.