Month: July 2010

Transportation energy use

Since energy is a topic of conversation in our office, and I have been doing some bicycle commuting, it suddenly became important to have a table of transportation energy use.

Mode kW-h/km kcal/mile Miles/gallon kW-h/mile beer-pints/mile
Bicycle 0.0361 50 629 0.058 0.23
747 0.2521 350 90 0.407 1.59
Electric Car 0.1550 215 146 0.250 0.98
SUV 1.5128 2098 15 2.440 9.54
Train 0.0820 114 277 0.132 0.52

Conclusions:

  • Bicycle wins the efficiency contest.
  • Electric car could win the efficiency contest if you fit 5+ people in your car.
  • Escalating that war, the tandem would probably be the next weapon of choice.
  • Trains are pretty good (no surprise), and perhaps could get better with regenerative braking.

Assumptions:

  • Bicycle uses 50 kcal/mile
  • 747 90 mpg (FAA figure is lower,but…)
  • Electric car: .25 kwh/mile (from Tesla  if you trust software ‘geniuses’  posing as a car company, or if you trust the old fashioned car company GM, their ‘Volt’ appears to be .34 kW-h/mile)
  • <rant> Tesla presents data like a software vendor (no surprise).  Their claim a 70amp @220 volt charger, running for 3.5 hours charges the battery fully (capacity listed as 55kw-h). Energy = efficiency (always less than 1.0) x 70 x 220 x 3.5 = 53.9. Clearly credibility = 1/ efficiency </rant>
  • SUV 15 mpg
  • Train (swiss) .082kwh/passenger-mile
  • Pint of beer has 220 kcal
  • kcal (kilocalories) are the kind we eat (aka Calories with a big ‘C’)  Yep, our system of measurement is THAT stupid. Small calories x1000 = Calories =  kilocalories.

Conversion Notes:

  • It’s assumed that all liquid fuels have the same energy content as gasoline: 36.6 kwh/ gallon.
  • Liquid fuels have crappy energy conversion, unlike electricity which can be 100% efficient.

Installation for attics with loose fill insulation

Loose Fill Insulation

We often get asked if AirScape whole house fans can be installed in attics with loose fill insulation. The answer is yes, with one additional install step. The idea is to stop the insulation from being displaced by the air movement generated by the AirScape. We now offer a breathable synthetic fabric that can be placed on top of the insulation to stop any displacement. The installation is as simple as laying the material down in the attic where the fan discharges and tacking or weighting it down. The final step would be to turn the AirScape on and adjust the fabric material as needed.

The Loose Fill Insulation Cover (LFIC) is available in 9’x10′ sheets and can be found on any of the product pages on the website.

Solar Loves Whole House Fans

There are a couple of trends that will affect solar photovoltaic installations:

  • Newer electrical rate structures encourage conservation (tiered rates)
  • ‘Energy Security’ is a powerful motivator
  • Photovoltaic rebates require house efficiency check-ups

We think  solar energy gathering is great. The idea of  getting electricity essentially for  free energy has certainly captivated our imaginations. Even though the cost of photovoltaic panels is dropping very quickly, the investment is still considerable.  Our crystal ball tells us that electrical energy is very, very versatile and will be in demand as electrical cars come on stream and coal fired electrical power plants start to show their ugly side. (coal burning)

As the demand for clean electrical energy increases, its value will certainly not go down.   In fact, if the validity of predicting cheap energy such as the famous line is any guide “too cheap to meter”,then we should get prepared for high prices.

By combining whole house fans solar contractors and  homeowners  can:

  • Decrease the initial investment in PV panels
  • AND/ OR
  • Increase the  Return on Investment for the entire system

sustainable budhism

The local buddhist temple has just been completed. AirScape provided several whole house fans. The building itself is constructed with ICF (insulated concrete forms). This makes for a high mass, well insulated and sealed building envelope, perfect for whole house fans.  Total airflow from the whole house fans is 9200 CFM – the building is 6,000 sq. feet. That’s a good lot of air, but this is the only form of cooling, so the amount of airflow has to be high for the peak conditions.

If you want to design your own temple, Carlos Delgado is the architect.

If you are considering a heat pump

This article by Henry Gifford, an energy saving specialist discusses why heat pumps are no panacea.  His points, well made, bring home the messages that building envelope efficiency is critical and the importance of examining the entire energy chain –  from power house to your house.  Not that readers of this blog need reminding, but Henry also points out that over half of this country’s electricity derives from coal burning . (BTW clean coal = oxymoron du jour)

www.energysavingscience.com/

http://www.finehomebuilding.com/departments/taking-issue/heat-pump-schmeat-pump.aspx