Monthly Archives: March 2013

“Crowd Sourcing” Energy Production

A company in Great Britain recently installed special tiles which generate electricity when pedestrians walk on them. The generated electricity can be used to light up the pavers themselves using high-efficiency light emitting diodes (LEDs) or wired to remote lighting or even be fed into the electrical grid.

An engineer by the name of Laurence Kemball-Cook came up with the idea and has established a company to exploit this technology. His company Pavegen manufactures tiles which are made of a combination of recycled concrete and rubber from recycled tires.
green-paving-slab

When one of the tiles is stepped on, the surface is slightly compressed about a 1⁄5 of an inch. This compression is converted to electricity via the piezoelectric effect (pronounced PIE-EE-ZO).

Actually, the work done to deform a crystal is converted to electrical energy. The effect is taken advantage in the igniters in stoves, barbeque grills, and cigarette lighters. The reverse effect functions to create the timing device in quartz watches. In this case an electric current is used to make the quartz crystal deform, that is vibrate. The frequency of the vibration is used to measure time.

This technology has applications wherever there is pedestrian traffic, indoor or out as the tiles are waterproof. Pavegen is currently installing its device in a pedestrian area adjacent to the stadium in London which will host the Olympic games this summer. Tens of thousands of foot falls will light up an adjacent mall. Numerous other applications of the technology include shopping malls, playgrounds, airports and train stations and urban sidewalks.
how-they-generate-electricity

If the piezoelectric tiles were placed in highways they could generate energy to power street lights, traffic control signals, etc. The energy could power devices which could warn motorists of the presence of ice on bridges and overpasses. The power could conceivably be used to warm the surface enough to prevent icing in winter.

Another application of the piezoelectric effect is being developed for shoes and clothing. The military has experimented with piezoelectric boots which could power personal gps devices for battlefield management. Civilian technology could include piezoelectric clothing — say a jacket or pair of pants which when worn and thus in motion could generate energy to charge a cell phone, a music player or even a portable computer. Until the advent of nanotechnology this has not been possible because the piezoelectric electric materials were too brittle to be woven into fabrics.

The solution to our waning supplies of fossil fuels and the attendant problem of global warming from the use of those fuels will require many ideas big and small to create clean energy and a sustainable future. All this energy from piezoelectric devices is not free. It comes from energy expended by the people wearing or stepping on them. In our overweight society, however, that may not be a bad thing.

Electric Highways and Byways

President Obama recently announced new fuel efficiency standards for cars and light trucks. By 2025 the Corporate Average Fuel Economy of these vehicles will be 55 miles per gallon of gasoline or its equivalent from other energy sources. It is unlikely that this standard can be met by sticking with the internal combustion engine. In fact the standard has encouragements built in which favor alternatives.

Foremost will be gas/electric hybrids, but plug-in hybrids and pure electric vehicles will contribute to the mix. Gas/electric hybrids such as the Prius gain efficiency and therefore higher mileage because they have batteries and electric motors to boost power when needed. The batteries are recharged from the gasoline engine when less power is required. Plug in hybrids and pure electric vehicles get some or all of their power from batteries charged from the electrical grid.

The greater simplicity and efficiency of electric motors mean that their mileage is much better than cars powered by internal combustion engines. Another advantage of electric cars is that the energy used to charge the batteries can be produced at locations remote from urban areas. This will have the effect of lowering pollution where people live and work. Overall less energy is needed to power an electric fleet of vehicles, regardless of how the energy is produced.

The significant advantage of gasoline powered cars is one of energy density and refuel time. A simple comparison is illustrious. A gasoline powered car can travel several hundred miles before refueling is necessary, and then the refueling time is only a matter of a few minutes. Currently available pure electric vehicles have a range of less that one hundred miles and recharging the batteries takes hours, not minutes. Research is ongoing to improve both the energy density and recharge times for batteries, but an alternative would be to charge the batteries on the fly.

This is the way a gas/hybrid electric works but it requires hauling a gasoline engine around with you. Ideally if you could charge the batteries as you go without a gasoline engine then the issue of battery life and recharge times becomes immaterial. We need a technological leap to get there but it should not be that difficult.

Enter microwave power transmission. Imagine a highway system with microwave broadcast antennas imbedded in the pavement. As electric cars drive over a segment of an antenna, computer controls on board would turn on the broadcast antenna, and a receiving antenna in the car would use the received power to charge batteries, essentially continuously. No power would be wasted as the broadcast antennas only function when a car is overhead and signaling to receive power. The system could begin in urban areas, extend to the interstate highways, and finally to the byways.

In all but the most remote areas, cars could still operate on batteries big enough to get them “off-grid” for reasonable distances, say a one hundred mile range. To minimize transmission losses, power could be provided from solar panels lining the highways. Or how about decking over the highways with panels? Both protect the highways and drivers from the weather and power the vehicles at the same time! I won’t go so far as to say the possibilities are endless, but there are a lot of novel ideas out there to be exploited.

Moon, Turn the Tides…

Moon_phases_en

“Moon, Turn the Tides” is one of the more evocative selections on an appropriately titled album, Electric Ladyland, by Jimi Hendrix. The selection and the album title are appropriate as the moon does turn the tides, and the tides can be used to generate electrical energy.

Tidal energy is one of the rare exceptions to the rule that all the exploitable energy sources on earth are directly or indirectly solar power. Fossil fuels are solar power stored via photosynthesis and collected over millions of years. Wind and hydropower are also derived from solar power. Modern architects incorporate passive solar design into homes in the same way that the American Indians of the Southwest chose south or southeast facing cliffs to exploit passive solar energy input.

The tides are unique in that they are driven by the gravitational pull of the moon on large bodies of water. Smaller bodies of water such lakes or even a glass of water will be impacted by tidal forces but the effects are ridiculously small. In locations where local geography allows, the tidal movement of water can be exploited as an energy source to generate electrical energy.

Two methods can be used to capture tidal power, turbines placed in the path of a rising and falling tide and tidal lagoons which are natural areas where a barrage (a small dam) can create a lagoon from the tidal flow. Release of the impounded water then turns turbines. Turbines that utilize the flow of the tide are simpler to operate but only produce power when the tides are moving whereas tidal lagoons are more complex but allow for time shifting to release the water, better matching energy supply with demand.

Because of the unique set of circumstances required for the exploitation of tides, capacity is limited. In North America the Bay of Fundy in Nova Scotia, Canada has a tidal lagoon with a capacity of 18 megawatts. This relatively small power production site is meant mainly as a test facility to examine turbine design and environmental effects of tidal power

The largest currently operating tidal power project is the Rance Tidal Power Station in Brittany, France. This is a 240 megawatt facility. Much larger facilities are in construction or planned around the world. In Great Britain, the Severn Barrage is planned to yield 8.66 gigawatts. Estimates suggests that twenty per cent of Great Britain’s electrical energy needs can be met through tidal power.

The largest project being considered is a huge barrage, covering some 20,000 square kilometers in Penzhinskaya Bay, Russia. If this facility comes to fruition, it will have a peak power of 87 gigawatts, equal to the output of over 50 modern coal fired power plants.