the solarcat brochure

SolarCAT is a

concentrated solar power (CSP) dish system using solar-heated compressed air to drive turbines generating on-peak power. Air is compressed with off-peak power at night when demand is low.

Solar dish fields are

built where compressed air can be economically stored up to 400 psi. Salt caverns, depleted gas wells, abandoned mines, aban-doned pipelines, tunnels, or other large geological formations are suitable for air storage.

Electric motor-driven air compressors operate at night to store air,

preferably from wind power, as wind power is cheapest at night when demand for energy is lowest. Power is generated during the day, by combining the stored com-pressed air with solar heat.

Phone: 603 601 0450Fax: 603 967 4027Email: [email protected]

75 B Lafayette RoadHampton, NH 03842

SolarCAT Inc.

The SolarCAT System

An Illustrated View of a SolarCAT Dish Field

Illustration of SolarCAT in an Urban Industrial Setting

During the day, the compressed air is fed through small pipes to each dish

in the field, where it is heated by the sun to 1700o F. The heated compressed air drives four small in-line turbines per dish at 120,000 rpm to generate power. In this way, the SolarCAT dish field adds sunlight energy to the energy stored in the com-

pressed air, thereby increasing the delivered energy by 66%.

A dish mirror (left) focuses the sun's rays onto an

engine-receiver that heats the compressed air to 1700o F. Heated compressed air flows through four small turbo-alternators (below, right) plumbed to the solar receiver (gray cone). Turbo-alternators use non-contacting air bearing (no oil) and can operate at

120,000 rpm with virtually no wear.

The SolarCAT power system has a useful life

of 30-40 years. Since they are geological in nature, the useful life of salt caverns or other air storage vessel is indefinite. Compressed air is stored and ducted to the power conversion equipment at ambi-ent temperatures, minimizing transport losses, and is heated sequentially by a recuperator and solar re-ceiver immediately upstream of the air-driven tur-bines. Cool, high-pressure transport of the working fluid (air) makes SolarCAT more efficient than the other methods of concentrated solar power (CSP).



SolarCAT Inc.

How SolarCAT Works

Five SolarCAT dishes generate one Megawatt. With three dishes

per acre, 1 GW of SolarCAT with air storage would require less than 3 square miles of land – less than half the land of other CSP. Smaller systems can be installed as well, from 5 MW and up, presenting opportunities for commercial users, rural communities, and tribal utilities.

A single salt cavern or gas well can provide enough air storage for 1 GW

or more of SolarCAT power. Thousands of GW of air storage capacity for SolarCAT can be developed in geological formations that are already known. These opportunities are now being studied by utilities for large scale projects in California, Iowa, Ohio, and other states.



SolarCAT Inc.

The SolarCATPlant Schematic

This diagram illustrates how the air compressors store the potential energy of compressed air underground. The stored air then flows to the receiver where it is heated by the dish, driving the turbo-alternators.

The diagram below shows how the SolarCAT System can store and then supply power during the course of a 24 hour day to match a typical utility demand curve.

The Power Stored chart shows three sources of power that can be used to drive compressors. The black line shows that utility power could be used when demand is low, from 0-to-6 and 18-to-24 hours (night-time). The red line shows typical wind production, highest from 0-to-4 and 20-to-24 hours. The light blue line is the photovoltaic (PV) production curve, an option in the future when PV prices lower.

The Power Delivered chart shows that SolarCAT would deliver firm power between 6 and 18 hours, primarily with sunlight. The blue line shows the use of gas, oil, or bio-fuel when there is no sunlight available. Even when fuel is used, it is in combination with the stored compressed air. The result is still a very high fuel efficiency, which can realize substantial fuel savings.



The Power Supply and Demand Curves

SolarCAT Inc.

SolarCAT will buy wind power between hours 0 and 4, and between

hours 20 and 24, where the wind power is at its highest output and lowest price. PV and other sources of green power can be used when not possible by other utilities, due to load leveling limitations making it available at a low price.

Not only does SolarCAT produce power, it also provides a form of

beneficial energy arbitrage. By buying power during periods of low demand and low cost – 4-5 cents per kilowatt-hour – and increasing it by 66% with solar input, the sale of this power at pe-riods of high demand and high cost can reach as high as 8-14 cents per kilo-watt-hour.

Other CSP Systems:

Unlike SolarCAT, the more com-

mon steam-based concentrated solar power (CSP) systems operate at lower tem-peratures and lose substantial energy in the process of generating power. Heating water or oil to produce steam to drive turbines, storage of energy in the form of molten salt, hot oil, or hot water, and cycling exhaust through a cooling system are all sources of energy dissipation. The lower operating temperatures of steam systems, as well as the numerous heat exchange steps, result in much lower effi-ciency and therefore higher cost per unit of power produced.



The SolarCAT System Versus Other CSP Systems

SolarCAT Inc.

Economic Efficiency

SolarCAT uses energy arbitrage. It buys power during periods of low demand and low cost – 4-5 cents per kilowatt-hour –and stores that power in the least costly manner. Then, SolarCAT increases that power by 66% and sells it at periods of high demand and high cost – 8-14 cents per kilowatt-hour. This is beneficial to utilities, and can be operated in response to local requirements.

Existing CSP systems sell only the power they generate, and suffer additional losses in any energy they store. Most impor-tantly, their efficiencies are lower, and as a consequence, they require far more mir-ror collectors and structure.



Benefits of the SolarCAT System

SolarCAT Inc.

Efficiency and Sustainability

The peak theoretical efficiency of a CSP plant is 50%. However, existing CSP systems such as solar trough are typically much lower in efficiency, and therefore use more land. In addition, CSP systems typically consume water for cooling, which is a barrier to their use in the desert.

Storage Efficiency

To deliver power on demand, CSP systems must have energy storage and/or fuel backup. These are the storage methods of current CSP systems:

SolarCAT stores air at ambient tempera-tures in caverns that can hold enough en-ergy for a day, a week, or even a year of operation. Caverns and other air storage vessels have virtually no losses of air pres-sure.

Power Tower systems store energy as hot water, oil, or molten salt, in containers that can hold a maximum of a 12 hour sup-ply of energy. This thermal storage inevita-bly loses energy through the insulation, and the pumping of fluids.



Further Benefits of SolarCAT

SolarCAT Inc.

Capital Cost & Time for Construction

SolarCAT systems enjoy an increase in daytime output due to the boost of stored energy with solar energy. This reduces the large-scale capital cost potential of a SolarCAT plant to about $1.0 billion per GW. Once a site is established and construction is underway, the installation rate of a large scale sys-tem is planned to be about 12-14 months per GW.

Existing CSP systems such as solar trough are currently costing about $4 billion per GW, even though the technology has existed for decades. Power Tower systems have yet to be commercially successful, despite decades of research and demonstration projects.



SolarCAT and Other CSP Technology Comparison

SolarCAT Inc.

Factors such as water use, efficiency, land requirements, and cost have presented economic and installation challenges to other CSP tech-nologies. SolarCAT is designed to overcome these problems.

The chart below compares SolarCAT to other CSP technolo-gies. Note that as fuel costs and commodity prices such as steel con-tinue to rise, the advantages that SolarCAT offers in much higher effi-ciency and low water use will provide increasing benefits over time.

CSP Comparisons

11

Trough/CLFR with Steam

Dish Stirling Power Tower CPV SolarCAT w/Air Storage

CompaniesAbengoa,

Acciona, Ausra, SkyFuels

SES, InfiniaBrightSource,

eSolarAmonix, SolFocus SolarCAT

CoolingWater cooling, or coolant/radiators

coolant/ radiators

Water cooling, or coolant/radiators air cooled

exhaust air at 120 F

Working fluids thermal oil, salt, water, steam

hydrogen thermal oil, salt, water, steam

none air

En ergy Storage

thermal mass (oil, salt, or water) none

thermal mass (oil, salt, or water) none

compressed air storage of off-

peak electricity

Efficiency 10-17% 20-30% 8-18% 15-33 % 30-37%

Minimum Unit 60 MW 25 kW 33 MW 1 kW 2 00 kW

Acres/MW 5 5 5 5-10 1.6

the solarcat brochure

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