Renewables can be introduced with locally installed PhotoVoltaic (PV) cells or solar collectors or by importing ‘green electricity’ e. g. from an off shore wind park. The latter however is not accepted within this project. The precondition we set for ourselves is that the investment for the installation generating renewable energy must stem from the renovation budget.

1.1.1. Application of Photo Voltaic

One option to reach the target is the application of PhotoVoltaic (PV) cells. Starting again from the middle bar in figure 1, the target can be reached by mounting 30-35 m2 of PV-modules of optimum orientation on the roof. However, for technical or architectural reasons this may not always be possible or feasible in renovation. In addition, it may not be very economical, which for Dutch builders is an important criterion. Financing constructions, e. g. leasing the PV cells from an energy supplier or an Energy Service Company (ESC) can help to overcome this barrier.

ECN is cooperating with 15 partners in the European ‘Crystal Clear’ Integrated Project aiming to reduce the cost of PV on a system level down to 3€/Wp, which roughly corresponds to an electricity price of €0.15 — €0.40 per kWh — depending on the location in the EU.

Assuming that any PV electricity not consumed can be fed into the grid, the application of PV does not interfere with other measures. The amount of PV, required to reach our target is therefore used as a measure of the success of other measures. This will be discussed in chapter 5 below.

1.1.2. Increased size of the solar collector system

As mentioned before, main consumers of electricity in a typical Dutch household are appliances such as a washing machine and a dishwasher, that can also be fed with (solar) heat (hot fill). However, solar heat is not always available when needed, especially in wintertime. There are two ways to maximise the contribution of solar heat: 1) to store the solar heat in a storage vessel until the time that it is needed and 2) to shift the moment of heat demand to the moment that solar heat is available. The latter could be achieved using smart control systems that would automatically switch on appliances like a washing machine, when sufficient solar heat is stored in the vessel.

The Dutch practice is to apply (if at all) a rather small solar collector, usually in the order of 3 m2 and a storage vessel of typically 150 l. These are rather modest sizes compared to the practice in e. g. German speaking countries, where collector areas are found of up to 15 m2 and storage vessels of up to 2m3 [5].

It is therefore interesting to see how much a larger solar collector system can contribute to the target of reducing the energy consumption by 75%. The scope of the simulations carried out is broader than just saving on electricity consumption; it includes savings on energy demand for space heating and DHW as well as the solar contribution to hot fill. The results of the simulations depend on the assumptions for the different parameters describing the system. These are briefly discussed in the following chapter.