The Xplore class tested their prototype solar updraft towers today--
Measuring the temperature with the infra-red thermometer:
We used a home-made rotor to test for flow:
Mr. Peloquin explaining project to exchange teacher from Beijing:
This one actually got quite warm due to it's height:
This team created a solar oven, which got the temperature up to 158 degrees:
Discussion:
What worked?
Why did the high cone one work the best?
What was something new you tried?
What would you do different if you had more time?
Options moving forward:
- Move on to the next project
- Re-design/iterate on your design
- Build one large one using the goal post as a chimney
Solar updraft chimney is a fluids problem-- air needs to infiltrate slowly enough that it is warmed by the time it gets to the chimney; tower needs to be tall and insulated to enclose a column of warm air- upward velocity proportional to height of hot air column.
https://en.wikipedia.org/wiki/Solar_updraft_tower#Efficiency:
Efficiency[edit]
The traditional solar updraft tower has a power conversion rate considerably lower than many other designs in the (high temperature)
solar thermal group of collectors. The low conversion rate is balanced to some extent by the lower cost per square metre of solar collection.
[18][43][44]
Model calculations estimate that a 100 MW plant would require a 1,000 m tower and a greenhouse of 20 square kilometres (7.7 sq mi). A 200 MW tower with the same tower would require a collector 7 kilometres in diameter (total area of about 38 km²).
[5] One 200MW power station will provide enough electricity for around 200,000 typical households and will abate over 900,000 tons of greenhouse producing gases from entering the environment annually. The glazed collector area is expected to extract about 0.5 percent, or 5 W/m² of 1 kW/m², of the solar energy that falls upon it. If a transpired solar collector is used in place of the glazed collector, the efficiency is doubled. Additional efficiency improvements are possible by modifying the turbine and chimney design to increase air speed using a venturi configuration. Concentrating thermal
(CSP) or photovoltaic
(CPV) solar power plants range between 20% to 31.25% efficiency (
dish Stirling). Overall CSP/CPV efficiency is reduced because collectors do not cover the entire footprint. Without further tests, the accuracy of these calculations is uncertain.
[45] Most of the projections of efficiency, costs and yields are calculated theoretically, rather than empirically derived from demonstrations, and are seen in comparison with other collector or solar heat transducing technologies.
[46]
The performance of an updraft tower may be degraded by factors such as atmospheric winds,
[47][48] by drag induced by the bracings used for supporting the chimney,
[49] and by reflection off the top of the greenhouse canopy.
- The atmospheric vortex proposal[50] replaces the physical chimney by a controlled or 'anchored' cyclonic updraft vortex. Depending on the column gradient of temperature and pressure, or buoyancy, and stability of the vortex, very high-altitude updraft may be achievable. As an alternative to a solar collector, industrial and urban waste-heat could be used to initiate and sustain the updraft in the vortex.
- Moreno (2006) teaches in U.S. Patent #7,026,723[51] that a chimney can be economically placed on a hill or mountain slope. Klinkman (2014) in U.S. Patent #8,823,197 [52] elaborates on constructing diagonal chimneys. A structure as simply built as a high hoop tunnel, but much longer in length and on a slope, can permanently generate an airflow for producing electricity. Changing the chimney's height differential from 200m (the Manzanares experiment) to 2000m (Charleston Peak in Nevada has a rise of over 2500m, for example) will transfer a factor of ten more of captured solar heat into electric power. Increasing the temperature differential between chimney air and outside air by a factor of ten increases the same chimney's power by one further factor of ten, assuming that the chimney's walls are engineered to take the extra heat. Concentrating solar heat is often done with reflection.
