Renewable Energy

Microgeneration & Embodied energy:
making sure you're genuinely saving energy

Embodied energy

Whenever you manufacture anything, you use energy. The embodied energy of a product is the total amount of energy required to dig up the raw materials, manufacture them into a product and deliver it to the place where it is used. Some examples are given in the table below.

USEFUL ARTICLES

Benefits of assessing embodied energy in buildings

Technology	Type	Embodied endergy	Efficiency	Cost
Solar hot water	Flat plate collector	500 kWh / m²	40%	£500/m²
Solar hot water	Vacuum tube	1000 kWh / m²	50%	£750/m²
Solar electricity	Crystaline silicon modules	2000 kWh / m²	10%	£650/m²
Solar electricity	Thin film plastic/metal	750 kWh / m²	4%	£280/m²
Wind	Domestic 2.5m blade 1kW turbine	3000 kWh	16%	£900

Source

Energy payback

If you add microgeneration, or any energy saving systems to your house, they will have to be working for some time before they have paid back the energy used in their manufacture. Until they have done so, they’re not really saving any energy at all.

So to find out if microgeneration is worth it in any given location, the person doing the planning must find out the embodied energy any proposed system and compare this to what it will actually generate in that location. An inappropriately chosen system may never recoup the energy used to build it.

Next: Is it worth it?