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Berkeley 2011 Day 2


The Rosenfeld Curve showing per capita electricity consumption in California compared to the rest of the country, from http://piee.stanford.edu/cgi-in/docs/publications/sweeney/Deconstructing%20the%20Rosenfeld%20Curve.pdf

Katey Walter Anthony, University of Alaska

Methane Release from Thawing Permafrost

  • As permafrost melts, microbes consume old carbon, producing CH4, which bubbles up and is released to atmosphere
  • There is a lot of carbon tied up in permafrost, mostly in Siberia and Canada.
  • In the Pleistocene (), there were cold winters and warm summers. Organic material generated during the warm summers froze and settled during the cold winters, so it didn't decompose. As it thaws, that carbon can be released again to the atmosphere.
  • Estimate: the carbon in Yedoma lakes: 24 ± 10 Tg
  • The radiocarbon age is 14--46 ka. There is younger carbon from holocene in lakes that aren't non yedoma
  • She made a claim I didn't understand, that the variation in the rate of methane bubbling up from these lakes is caused by variations in atmospheric pressure. We discussed this briefly in the corridor, but I still don't get it.

Peter Schwartz, Cal Poly San Luis Obispo

  • http://www.gapminder.org/ --- fun!
  • Londoners accepted congestion pricing because they saw it was reasonable (unlike London traffic)
  • What about getting some bus rapid transit in L.A.?

http://www.eere.energy.gov/buildings/appliance_standards/

Over ? time, highway spending outstripped public transit by more than ten to one. Also claims that we would need to raise the price of gasoline by five times to cover the true cost of externalities.

Philip Haves, modeling buildings

Standards affect more than 80% of residential construction and over 60% of commercial construction. In the past year or two, TVs and set tops have surpassed refrigerators in the amount of energy they consume. The national average electricity rate is 0.094 $/kWh. Information about appliance efficiency standards may be found at http://www.eere.energy.gov/buildings/appliance_standards/

Refrigerators

LBNL looked at the performance of refrigerators in 1990 and determined that all existing refrigerators had one "good" component and the rest were lousy. So, they issued the 1993 standard that none could meet at the time. Within the three years all manufacturers did meet the standard and it was cost effective to do so.

Appliance efficiency is a real example of government working for the common good. For an investment of $300 million in research and standards development the public saved $48 billion.

Recent innovation: Sun Front has developed a more efficient refrigerator/freezer by having separate compressors for the freezer and the refrigerator. In a "standard" LCD television, only 5--7% of the light actually emerges. http://ees.ead.lbl.gov/

Texas wind cannot transmit enough power from wind farms to the major cities to keep from dumping some of the power.

DC high-tension lines have lower loss (because they don't radiate). Of course, you have to convert on both ends, so that loss has to be factored in. Needs research and development of semiconductor power electronics.

George Crabtree, APS Study on Integrating Renewables on the Electricity Grid

  • Roof area is about 6 billion square meters, which would generate about 600 GW. Urban footprint: 3% of land, ~2300 GW ?
  • There is a big electrolysis effort in Scandinavia, with 80% efficiency, generating hydrogen.
  • The problem with high-Tc superconducting transmission lines is that the cost to cool them is half the electricity savings.
  • Mason Willrich, Electricity Transmission Policy for America (2009) Study on upgrading America's electricity grid
  • In Xiang, China a 6 GW, 2000 km DC transmission line is being constructed. It operates at 800 kV. Such lines use less metal than AC lines, since they avoid the skin effect, and have lower radiation and corona loss.

Walter Musial, Offshore Wind Power (NREL)

  • 9 GW of offshore wind being developed in the middle of the North Sea
  • The Cape Wind power purchasing agreement is at 0.18 $/kWh. If it could be reduced to 0.14 $/kWh it would be useful.
  • Offshore wind equipment is almost the same as onshore, with a few tweaks for the more corrosive environment. There is a push towards larger devices. Another difference is greater mass for the tower.
  • Roughly speaking, the power output is {$P = \frac{1}{2} \rho A u^3 (\eta_{\rm mech} C_P)$}, where {$C_P$} is bounded above by the Betz limit (59%). Current values for the best turbines is 51--52%, so there isn't a lot of room to improve there. However, scaling up the diameter of the turbine is tricky. The flap-wise load scales is {$R^3$}, but the edgewise load scales as {$R^4R}. Fifty-meter blades are common on shore. Current big offshore turbines have a diameter of 126 m.
  • On land, it is important to keep the blade tip speed below 80 m/s for noise considerations. Off shore, it can go up to 100 m/s.
  • One possibility to lower cost might be to go to two blades instead of three.
  • Above 5 MW, direct drive generators dominate; below, gearboxes.

Photovoltaic Roof Systems, Ben Bierman (Solyndra)

  • http://www.solyndra.com/
  • CIGS solar cells in tubular form to be mounted above white roofs. The cells feature a 15-mm tube inside a 22-mm tube filled with suitable index matching fluid to focus light into the inner tubular cell
  • 11 billion square meters of commercial flat roofs
  • Title 24 requires cool roofs in California
  • Rooftop power competes at the retail electricity rate, not the utility's generation rate
  • In the fourth quarter last year they produced 22 MW of cells, with a total of 100 MW installed
  • They had 1.5% of a 4 GW market in 2010
  • 7--8 year payback period
  • European photovoltaic systems typically operate at 1 kV; American ones at 600 V. Ours, therefore, require about 50% more wire.

Photovoltaic Concentrator Systems, Steve Horne (Sol Focus)

  • http://www.solfocus.com/en/
  • There are about 20 players in concentrating photovoltaics
  • They use a Cassegranian approach with about 650x concentration
  • Has a 1.75° acceptance angle, which means there are no alignment problems
  • Glass has 5 times lower embedded energy than plastic.

Topics in Nuclear Power: Small Reactors and Nuclear Waste, Robert Budnitz (LBL)

  • One-quarter of worldwide nuclear reactors are in the United States
  • How does the industry improve safety?
    • Probabilistic analysis of accident scenarios [I wonder if those scenarios included the Fukushima Daiichi disaster?!]
    • Gathering data on all "events"
    • People at different power plants compare best practices
    • Operators undergo training every 5 shifts
    • No-fault reporting
    • All mishaps throughout the world are shared among the community, so everyone learns from each mistake
  • The number of incidents has dropped by a factor of 10 over the time period 1988 to 2003
  • Forced outages down to 1%
  • Management change has led to maintenance workers worrying about systems and suggesting improvements
  • There is a diseconomy of scale with large plants. Smaller ones (100 MW) may be easier to manage
    • Cooling is easier
    • Simpler to operate
    • Can use natural convection cooling
    • Factory fabrication, with rail transport
  • Dry cask storage in large concrete silos 25 feet high is good for at least 50 years; not good for 2 centuries
  • The total cost to build Yucca Mountain would be 1--2% of all electricity generated
  • Claims that pebble bed reactors are too expensive