Primary energy Renewable

Those fiendishly clever souls at the Passive House Institute have deigned to make a complicated subject even more complicated. To be fair, they have a point. Primary energy (see previous entry) is useful, but it's problematic too. Take renewable energy sources such as wind, solar and hydro or tidal. Primary energy figures give these sources a score of 1.0, meaning its regarded that 1 kW of, say, wind energy used in the building, took 1 kW of wind to generate it. (The implication is that waste of renewable energy doesn't matter, which troubles us). But of course, the reality is more complicated. In reality, these energy sources have one big limitation: intermittency. And because, say, the wind isn't always blowing or the sun isn't always shining sufficiently to generate electricity - either via the grid on microgeneration - exactly when people need to have a shower or turn on the heating, there are inefficiencies to contend with. In addition to grid transmission losses, this includes storage losses. So for this reason, the Passive House Institute now has two primary energy metrics that can be used: primary energy, and primary energy renewable (PER). PER takes account of the additional renewable energy required to be generated to provide the renewable energy required for specific uses in a building.

For a better explanation, click here.