Within the Energy Performance of Buildings Directive the Primary Energy Factor (PEF) is used when calculating the energy performance. The PEF accounts for the energy losses of electricity generation and transport when comparing electricity use with other types of energy use in the building. But a recent Ecofys study warns that PEFs are not an unambiguous scientific value. Edith Molenbroek, researcher at Ecofys said: “Calculation methods are not transparent, harmonised and consistent and are not always adjusted to higher shares of large-scale renewable electricity.”
These are the main conclusions from the study Primary energy factors for electricity in buildings’ (May 2011), executed by Ecofys. The PEF was originally intended to compare the burning of fossil fuels in a local burner with electrical energy generated in fossil fuel power stations. However, once a significant share of the electricity is generated by renewable energy, the concept of primary energy loses value.
That said, when evaluating the energy performance of buildings, a correction factor penalizing the energy losses in the electricity system is still required. The Ecofys study recognizes this, but argues that the PEF should be taken for what it is: not an unambiguous scientific value, but rather a political instrument intended to maximize the contribution of buildings to a sustainable energy economy.
Being a political value implies that it can be calculated in different ways. Ecofys studied the PEF calculation methods used in seven EU Member States and demonstrated a lack of consistency. “In certain Member States, we could not discover the underlying calculation procedures at all”, said Molenbroek.
Since various calculation methods are being used, their effects and the consequences of each of them should be evaluated very carefully. Ecofys studied the extent to which the PEF can stimulate energy efficient buildings, the use of local renewables, and centralized renewable power. It demonstrates that those goals can oppose each other when defining the PEF calculation method, and describes solutions to get around such conflicts.
One of the undesired side effects could be that the high PEFs (compared to the given electricity supply mix in that country) used by some EU Member States may hamper the development of grid coupled renewable energy in the long run. A high PEF for renewables (e.g. > 1 in Spain and Sweden) leads to a high average PEF, even in a country with massive deployment of renewable energy. As a result, the small amount of heating energy that is still required in low energy houses tends to be supplied by local fossil fuel burners instead of using the increasingly renewable grid electricity. It also prevents using the storage capacity of electrical heating systems as a buffer against the intermittent nature of renewables, which could jeopardize further growth of grid-coupled renewable electricity.
This example of negative feedback shows that a dynamic approach for the PEF is required, as the energy mix for electricity generation is expected to evolve drastically in the upcoming decades. The Ecofys study recommends re-evaluating PEF calculations at regular and timely intervals and adapting them to changing needs and circumstances.Log in to post comments