4/17/2008 - A Carbonless Energy Strategy, Architecture and Design

Updated: 4/17/2008

A Carbonless Energy Strategy, Architecture, and Design

David Spicer

Overview

In a world beset with problems ranging from energy shortages, pollution, global warming, climate change, terrorism and wars purported to defeat it, one problem stands out: our addiction to burning fossil fuels for their energy content. The reason, of course, is that eliminating this addiction will make these and other issues vanish.

This document proposes a strategy for achieving a national carbonless energy future. There are many “moving parts” to such a strategy but hopefully, a country as sophisticated as ours can learn to “walk and chew gum” at the same time. The goal is to publish a consistent strategy utilizing these moving parts that could be a starting point our leaders could take up.

This is a working document that was initially seeded by the outline used in my novel DEADLY FREEDOM. The first component of the strategy is an architecture for providing a carbonless energy economy. The proposed architecture will be built out of existing technologies, no “leaps of faith” or “science projects” requiring people in white lab coats will be required. I will reference the companies best positioned to provide the technologies and provide links to their products/services where appropriate. We have all the required technologies at our disposal today! The question will be cost and this is discussed in my post “A Business Proposition for America.”

Architecture

The architecture of any energy economy has three primary components: energy sources, energy sinks (the users of the source energy), and energy distribution to connect the sinks to the sources.

In our current carbon-based fossil fuel environment, the vast majority of our source energy is provided by oil, coal, and natural gas, with some nuclear and some hydroelectric. Our energy sinks tend to be almost entirely carbon-based, including the cars we drive, the trucks we use for deliveries, and the furnaces we use to heat our homes and run our factories. Oil and gas distribution utilizes carbon for trucking and shipping, and all too often we spill the contents of what’s being distributed! The Exxon Valdez is the single most ominous example and more recently, there was the explosion in New York of a train carrying propane and an oil spill in San Francisco Bay.

By contrast, in a carbonless energy world sources, sinks, and distribution, are completely devoid of fossil fuels. But we have competing architectures that could provide a carbonless path; it comes down to a Hydrogen Economy vs. an Electric Economy (although hydrogen fuel cells can be considered just batteries, which tends to cloud some issues). The problem is that we may not have the luxury of time to build and test each solution. We need to do some analysis to pick the right path, or to do some, as Einstein called them, gedanken, or thought experiments.

In my overview of an Electric Economy, I discuss hydrogen concerns, mostly in the area of handling and distribution. Before I started my research I began with the preconceived notion that the result would be “The Hydrogen Economy.” Fuel cells charged with hydrogen that produce just electricity and water when the energy is released are a very seductive technology, very futuristic. But the practicalities of the existing electrical infrastructure versus no existing infrastructure for hydrogen pulled me away.

Implementing the Architecture

At this point I conclude that our energy source will be generating electricity; that all of our sinks, or uses of energy, will be electrically powered; and, of course, the distribution connecting these two will be based on the existing electrical grid. But we still have many choices to make and issues to contend with.

Generation

Clean electricity generation can come from a variety of sources including nuclear, solar, wind, and even tapping into the power of oceanic waves. We aren’t constrained to pick just one source, the answer may be in harnessing more than one to take advantage of unique characteristics. Even then we have choices. For example, solar energy can generate electricity thermally by heating water into steam to turn a turbine; or using a photovoltaic process, by converting sunlight directly into electricity—photons to electrons. Each has certain benefits over the other. My assumption at this point is that both forms of solar will be used. While photovoltaic is a good match for business and residential rooftops to offset electricity costs, solar thermal looks most promising for integration with existing electric utilities that have the embedded plant for distribution to our homes and businesses. Utilities are accustomed to dealing with steam turbines, homeowners are not. A new player in the solar thermal space is Ausra, a Palo Alto startup that has moved from Australia to the US. The major benefit of solar thermal for utilities is the ability to store energy thermally for 24-hour operation. Ausra’s technology is unique in that it uses lower temperature steam (about 300 degrees Celsius, or 572 degrees Fahrenheit) and matching lower temperature turbines that were developed for the nuclear power industry. Storage of super-heated steam is in underground tanks at a pressure of 1200 psi.

Using solar thermal technology we can establish a “solar furnace” comprising 150,000 square miles of mostly unusable space in the southwest where they experience 80-100 percent of total possible sunshine. It should be noted that most of this land is already owned by the federal government. Since it would take 12,000 square miles to provide our entire current electrical load, this area could provide all of our energy for many generations to come, or power 12 countries our size today.

Electrical Loads

As for our electrical loads, our uses of energy, we can heat our homes, cook our food, run our factories, and now power our cars with clean electricity. The breakthrough for electric transportation is lithium battery technology in various forms. Lithium is the lightest metal but like anything else, there is not an unlimited supply. It would be a shame to trade oil shortages for lithium shortages. Fortunately, lithium is recyclable by companies like Toxco who have had a patented process in place for years. In terms of deployment, electric vehicles are just now reaching the market, four such vehicles come to mind, cars from: Tesla Motors and ZAP in the US and Lightning Car Company in the UK. Most recently, GM has announced an entry in the market called the Chevy Volt. We can accelerate their introduction by mandating that a percentage of the new cars and light trucks that manufactures sell in this country must be “40 mile capable” EVs and at the end of five years, all such new vehicles must be EVs.

Distribution

As for distribution, the US power grid is in place and could be used as is initially. But if we are to add to its responsibilities the requirement that it distributes our energy for transportation, then we need to give serious thought to upgrades.

As we tap into alternative forms of centralized electricity generation, we will need to distribute that electricity much farther than we do today. An approach to doing that is shown in the picture above. This map is from the North American Electric Reliability Corporation, NERC, the non-profit corporation chartered with the oversight and coordination of the current eight distribution regions depicted. Overlaying the NERC map I have superimposed the “solar furnace” this country is fortunate to have. Since optimal solar power is mostly concentrated in one geographic region, we need to transmit that power to each of the exiting NERC regions which can then distribute internally as they do today.

An appropriate technology for this distribution will be the use of high capacity High Voltage Direct Current (HVDC) transmission lines as shown by the red lines in the figure above. The advantages of this technology over traditional AC transmission used within NERC regions include:

1. losses per unit of distance are about 50% those of AC,

2. Firewalling. Connecting regions with AC transmission would require synchronization of the regions.

3. Full use of the conductor, avoiding the “skin effect” of AC and thus lower losses for long distances.

When daily power peaks are taken into account, my calculations for the US show that providing all of today’s 4 trillion KWH annual electricity usage would require a generating capacity of 1000 Gigawatts. If we start by eliminating the oil we use for transportation then we would need to add 100 GW of capacity that would require about 1200 square miles of thermal solar panels in the desert. Since this would need to be distributed to the eight NERC regions, I have defined a modular ”power chunk” of 10 GW as the basic unit of generation and transmission. My choice of 10 GW is somewhat arbitrary based on the world record HVDC transmission system in Brazil, where they transmit 6.3 GW of power about 800 kilometers. Fortunately, our full capacity does not need to be delivered day one and can evolve over time. The point is, we can have an architecture that scales well into the future. Our transmission lines would be of varying lengths, but a conservative average would be 1500 miles, with the longest lines being 2500 miles.

Then there is the issue of security. The power grid is already a national resource that needs to be protected. Adding transportation energy distribution makes it more so. We must harden this critical infrastructure from both physical attack, and as shown recently, cyber attack. Should we consider nationalizing the power grid, or at least the HVDC portion of it? As an avowed capitalist, this is difficult to fathom, but given the criticality of this resource and the need for standards and security, it’s at least worth considering!

A 24/7 Solar Thermal System Design

In this section I will provide a generic solar thermal system design capable of delivering 1GW of power 24 hours per day, 7 days per week. I start with the array design, then storage design. I will then use that system as the basis for building up a 10GW system and then a 100GW system. Note that this is NOT a detailed design that would take into account such things as hourly variation in load. This is a high-level design to demonstrate feasibility. The choice of 1GW as the basic module size is driven by the economic availability of steam turbines at that size. As steam turbine technology advances, the base module size could be increased proportionately.

Assumptions:

1. Average solar intensity between 8 AM and 4 PM every day: 1kw/m²

2. Efficiency of solar array: 10%

3. Thermal array output vs input water temperature in centigrade: 150

Array Design

An array that powers a system generating 1GW 24/7 needs to generate three times that, or 3GW, during the 8-hours the sun is shining.

So a solar thermal array of 11.5 square miles will generate 3GW of power for 8 hours per day.

Storage Design

Since we will be relying on heated water storage for 16 hours per day and that storage must also generate 1GW for that period, we need 16GWH of water storage.

Using the specific heat of water we have the following equation:

Where ΔT is the difference between the temperature of the water coming out of the solar array and that of the water returning to the array from the storage tank.

Since we want to find VOL in terms of Energy and Temperature, we need to solve for VOL:

But we need to cast this equation in GWH and cubic meters, not Kilojoules and liters. So to do that we must multiply the right side by the conversion factor for KJ per GWH, and divide by the conversion factor for liters per cubic meter:

Now plugging in 16 GHW as the required energy and 150 as the temperature differential:

So we need approximately 90,000 cubic meters of water to store 16GWH of energy. This would be a cube about 45 meters (approximately 150 feet) on a side.

Now we can consider constructing a 1GW solar thermal power module in the desert that would look something like the figure below.

Here we have the solar array laid out in a square 3.5 miles on a side. All of the heated water in the receiver tubes depicted by the heavy black lines is dumped into the storage tank and used to run a standard steam turbine that generates 1GW of power.

By combining ten of these 1GW modules we can construct a 10GW module as shown below.

Now we have the ten individual 1GW outputs running to a 10GW bus leading to an HVDC converter allowing power to be transmitted in DC form from this point on. This 10GW module would provide enough energy to charge 10 percent of our light duty vehicle fleet.

The last step is to grow multiple 10GW modules into a 100GW module that would be sufficient to power all of our light duty vehicles when they become EVs.

When viewed from space, this configuration might look something like an integrated circuit! However, this 100GW array would be a square of desert taking up approximately 35 miles on a side, or 1225 square miles. All the individual HVDC lines from the 10 10GW sub-modules would be collected in the HVDC Distribution center and routed from there to the existing NERC regions. Of course we could continue to deploy ten more of these 100GW modules to provide all of our energy in this fashion.

Economics

Needless to say, adding 100 GW of clean electricity generation to our infrastructure will be an expensive proposition. But as I discuss in “A Business Proposition for America,” these costs will be quickly offset by the hard-dollar savings generated as we wean ourselves off oil. Beyond that, the establishment of an Electrical Economy can stimulate our economic growth as discussed in “The Next Internet.”