Saturday, May 02, 2015

Fossil Fuel Lifestyle on a Renewable Budget

Frank Jotzo and Luke Kemp, from the Australian National University, produced the report "Australia can cut emissions deeply and the cost is low" (2015) for the World Wildlife Fund. That is a bold claim to make and, as I encourage my sustainability students to do, I thought it worth doing a back-of-the-envelope calculation to see if it is possible.

Jotzo and Kemp suggest Australia can be carbon neutral by 2050 though:
  1. "Ambitious energy efficiency improvements throughout the economy.
  2. Low carbon electricity supplied by either 100% renewables or a mixture of renewable energy and carbon capture and storage (CCS).
  3. Electrification and fuel switching towards biofuels and gas. 
  4. Reducing non-energy emissions through carbon farming and forestry, process improvements and CCS in energy intensive industrial applications."
But rather than make a whole of nation calculation, can a single householder maintain their lifestyle and be carbon neutral? The back of my ActewAGL electricity bill indicates that a one person household uses about 10 kWh of electricity a month.

A Nissan Leaf electric car has a range of 117 km with a 24 kWh battery, or 0.2 kWh per km. The average car is driven 12,881 km a year, or 1,073 km a month, which would require 220 kWh.

Assuming your job takes another 2010 kWh per employee per year, or 168 kWh a month.

That is in total, per month:
  • Home: 10  kWh
  • Transport: 220 kWh
  • Job: 168 kWh
  • Total: 398 kWh

Annual average solar radiation for the least sunny parts of southern Australia is 12 MJ/m2 per day, or 101 kWh/m2 per month. Assuming photo-voltaic system with 15% efficiency, this would be 15 kWh/m2 per month.

So the householder would need 27 m2 of solar panels. A modest one bedroom, one story home would have a roof area sufficient for this and so be able to generate enough energy for a reasonable Australian lifestyle.

Please note that I have not allowed for the energy needed for food production, manufacture of goods or their transport, nor losses for storage of energy. But also I have not allowed for the savings in energy from multiple dwelling households and use of public transport.

Also there is the issue of cost. Assuming PV solar panels cost $2,000 per kW (including installation) and get 3 hours of peak sun a day, producing 91 kWh a month. To power the single dweller's lifestyle will cost about $8,700 in PV panels. However, if these were installed as part of a manufactured home's roof the cost may come down to $4,400 (and lasting 10 years).

But the householder will also need batteries to store energy, which is where renewable energy becomes expensive. The 24-kWh battery pack for a Nissan Leaf costs $6,500 and is expected to last 8 years. The householder will need 13 kWh a day, even when the sun is not shining. Enough batteries for three days electricity supply would cost $10,600, or  about $111 a month.

However, this all assumes no energy saving measures, which Jotzo and Kemp point out can make a difference. As an example, while the typical one person household in Canberra uses 10 kWh of electricity a month, my energy efficient apartment uses about half that. Also I can walk to work, at my home office or corporate office, most days and so drive my car about one tenth the national average. As I need little more than a computer, my workplace uses about one half the amount typical. Adding up all this, per month:
  • Home: 5 kWh
  • Transport: 22 kWh
  • Job: 76 kWh
  • Total: 103 kWh
This would require a 7 m2 PV panel costing $2,300 and $2,700 of batteries, or $48 a month. There would be enough room on the roof of an three story apartment block for the solar panels to power each apartment.

The above figures are approximate "back of the envelope" calculations. However, they are relatively conservative and suggest a comfortable Australian lifestyle could be carbon neutral using current technology.

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