Abstract
Greensburg
On May 4, 2007, Greensburg, Kansas was struck by a devastating tornado. Approximately 85 percent of all standing structures were destroyed. Ten people were killed and many more were injured. The citizens of Greensburg used this opportunity to establish a new direction for their city. They initiated a plan to build a “green” city and provide inexpensive energy that would attract industry and growth. With the help of skilled architects and engineers, they thought of innovative ways to integrate new technology and make the city sustainable and a safer place to live.
The main power source for Greensburg is solar thermal energy from power plants located in the Mojave and the Sahara Deserts. The power is transmitted by microwaves to a satellite and then to a receiving center. The receiving center rotates to follow the satellite and collect the microwaves. Greensburg also generates power by harnessing its wind resources. The city’s excess power is sold to neighboring communities. Nanotechnology plays a key role in the distribution, monitoring, and control of the power system.
Greensburg provides personal and mass transportation by a pod system. A pod is similar to a car except for its circular shape. The pods are GPS directed and travel through a complex system of underground tunnels. Greensburg reserves its previous roads for pedestrians, bicycles, and emergency vehicles.
Greensburg’s environmentally friendly energy industry and its urban lifestyle are the primary reason for attracting 100,000 people to the city. People enjoy the fact that most of their favorite shops are just a five minute walk away. The city also offers ample civic benefits like schools, parks, and fire/police departments.
Although Greensburg added a variety of new attributes to its economy, it wanted to preserve some of its agribusiness and older structures. Greensburg has become a leader in genetic engineering. Recent discoveries of innovative ways to use corn for treating cystic fibrosis and Huntington’s disease have earned them international recognition. All of the crops that were used in this breakthrough were grown and developed near Greensburg. The grain elevator that survived the tornado now serves as a tourist center and museum. It stands as a reminder of how Greensburg got to where it is today.
One of Greensburg’s goals is to treat each drop of water as a precious resource. To achieve this goal, the city created a dam on an existing flood channel to form a reservoir. An ornate cooling tower serves as the center piece of the Greensburg’s most popular park near the reservoir. The cooling tower saves energy by making the city’s air-conditioning and heating systems more efficient.
Greensburg’s population has exploded from 700 to 100,000 over the last hundred years. As tragic as it was, the tornado gave Greensburg a chance to revolutionize its way of living and it is now at the forefront of innovative energy and transportation systems. With its civic benefits, transportation, renewable energy and urban essence, Greensburg has given a new twist to the expression “We are not in Kansas anymore!”
Essay
Greensburg
When Greensburg, Kansas emerged from the damage of a destructive tornado, the town recognized the opportunity to rebuild with green energy sources. Since the most abundant natural resource was wind, Greensburg harnessed the wind to provide power for the town. Supplemental power, needed in times of low wind activity, was generated by conventional fossil sources. As Greensburg grew rapidly, additional demands for power were met by clean solar thermal plants. With the help of nanotechnology to monitor our systems, we are able to produce a sufficient amount of energy to please the growing town of Greensburg and sell excess power to neighboring communities.
To generate a sufficient and continuous amount of electricity for Greensburg, two solar thermal towers are strategically placed in the Mojave and Sahara Deserts. These solar power plants consist of a chimney one kilometer high, and a greenhouse building around the base of the chimney. The greenhouses have black floors which absorb sunlight, collecting and storing thermal energy. The chimney effect causes super-heated air to rush upward turning wind generators. A microwave generator at each power plant converts the electricity to microwaves. The microwaves are then transmitted to the geostationary satellites, where they are redirected to Greensburg and are converted to electricity by a rectenna. The electricity is then distributed by underground power lines to meet consumer demands.
This is a complex power system. It has critical components in two deserts, two satellites, and one receiving tower located in Greensburg. Implementing nanotechnology to monitor and maintain the satellite protects our critical power source.
The power system is controlled by a distributed control system (DCS) that includes components at Greensburg, on the geostationary satellites, and at the power plants. Nanosensors are used extensively in the satellite because of their negligible weight. Nanosensors at the satellite optically monitor the path of the microwaves and measure temperature and stress points in the satellite. Nanosensors send signals to the DCS so they can be interpreted to optimize the location of the satellite and the orientation of the receiver on the satellite. Optimal orientation of the satellite is achieved by the DCS sending signals to actuators so the actuators can position the microwave receiver or activate impulse engines that move the entire satellite to a more optimum position.
The control system continually evaluates the overall efficiency of the power transmission and the integrity of the satellite to ensure the power needs of Greensburg are met without harm to the satellite. As an example, although microwaves can pass through clouds with acceptable losses, the system is optimized if the microwave path avoids these clouds. We use optical nanosensors that monitor the current microwave path from the solar thermal plant to the satellite, and from the satellite to the rectenna. This gives the DCS the information it needs to locate the optimum path and position the satellite accordingly.
Although nanosensors are used throughout the satellite to monitor key variables, the most innovative use of nanosensors is to measure the stress level in the receiver. Recent breakthroughs in material design have allowed receivers of the size required for microwave transmission to be practical for use in satellites. While it is strong, its strength is not unlimited. Threats such as space debris, radiation from the sun creating hot spots that result in thermal forces, and the distribution of the microwaves of the receiver can escalate the stress on particular points of the receiver beyond acceptable levels. Using nano-scale strain gauges, it has become possible to measure strain at a molecular level at thousands of key locations in the receiver. Each strain gauge contains a nano-scale wireless transmitter that sends signals to the DCS. The DCS calculates stress levels and determines if the satellite is within its allowable stress at all locations of the receiver. The DCS sends signals to the actuators and impulse engines so that the satellite and receiver can be reoriented so that no points on the receiver are over stressed.
Greensburg has created a reliable power system that continuously provides electricity to sustain a growing population with few negative impacts on the environment. Breakthroughs in nanotechnology and their application by control, structural, and nano-engineers have fulfilled a dream of a dependable power system.
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