Passive House – On-grid or Off-grid?
By Prof. Dr. Wolfgang Feist, Building Physics, Emeritus at Innsbruck University
Founder of the Passive House Institute
June 1st 2020
On-grid or off-grid is not an inherent part of the Passive House standard [PHI 2016]. You can do whatever you want. That said: Our recommendation is to install renewable generation as part of your project and to connect to the grid.
1. Why not inherent? Because it is of minor importance. The solution of the climate-crisis is to reduce climate-gas emissions as far as possible (to almost zero in 50yrs) [IPCC 2018]. This is best done by improving efficiency (a factor 10 is achievable [Feist 2007]). Passive House concentrates on this potential.
2. The remaining energy demand is very low and can be covered sustainably with available renewable resources. But to reach the goal of a fully renewable energy supply even faster, we support increasing the renewable energy capacities as part of each building project [Grove-Smith 2015].
3. We recommend installing a maximum of PV at every worthwhile opportunity - and that is, e.g. building or refurbishing a roof. You'll need a new cover anyhow. This can be PV, it won’t be much more expensive than any other cover and we recommend this.
4. PV without grid connecting would be a waste of investment, especially for large areas of PV-systems; but we need these areas, to meet the total demand of renewable energy generation for all the purposes a civilization has. Now, this WILL create a lot of excess power generation during daytime in the half year including summer. If we waste that, the economy of PV will crash.
5. We could: Install large capacities of individual storage (batteries). Whilst that’s quite expensive it is doable to cover 6 to 10 months of the year, depending on the climate. For the remaining time, an off-grid solution would need additional backup – and that’s another expensive investment [Kriesi 1990]. Doable, but: It will need traded energy carriers, e.g. plant oils – and here we are, again, faced with limitations due to broader sustainability issues. That, in a nutshell, would be the offgrid solution. Our assessment: That’s only a feasible path for an exceptional situation, such as a free standing single family home in the mountains. A bit tricky and nonsensical in cities like Beijing or New York.
6. The alternative: To connect to the grid is not expensive and the grid is just there, almost everywhere. So we recommend to connect to it.
7. Now: If the Passive House building is connected, it will be a very good “grid-citizen”: Even in maximum load heating condition (“the coldest day”) a Passive House can be without active heating for at least a day (up to 5 days) without anybody noticing a decline in comfort [Passipedia 2014]. That's due to the very long time constant coming with good insulation. In ordinary buildings heating makes up in maximum load conditions 85% to 98% of the total load; and in a Passive House still 30 to 60%. So, shifting the power drawn from the grid for 10 to 30 hrs is an option given by Passive House buildings during the time when it is needed most (heating period); as long, as the installed power in the Passive House is higher than the expected peak load without load shifting (which might be in a range of 500 W to 2000W for a standard dwelling) [PHPP 2015].
- The elitist affection of some utilities is a major reason for some people to go off-grid. As explained above, this is possible, but is not the best solution.
- Off-grid would be a second-best solution. A democratic grid-structure with a shared responsibility of generation and consumption would be much better; less expensive and more integrative. I used to say: A bit of trade is always a healthy ingredient of a well working human society.
- Each member of a democratic grid will be both: A supplier (e.g. at a time with high solar radiation) and a user (at other times). The grid will serve both in an optimal way in the sense that the suppliers can sell their power and the users can enjoy the energy services.
- For the individualistic “off-grid” solution a lot of elements are still to be discussed (e.g. how that could even work for a 10 Billion planetary civilization; not only technically, but also for living together).
- Also for the sharing, purchasing and optimisation of electric energy form a grid which is democratically organized, there are other aspects to be discussed and resolved (e.g. why a corporate solution will not work, what the “rules” in such a grid would look like and how that transformation can be made).
Passive House actually is a prerequisite to both potential solutions, whether on-grid or off-grid. During the transition period from the contemporary situation to whatever of the two solutions, improved efficiency is key. On a technological level the high power demand of winter heating makes affordable off-grid solutions for everybody impossible. And the same high power demand of heating will overwhelm any electricity network.
|Feist 2007||Passivhäuser in der Praxis, in Nabil A. Fouad: Bauphysikkalender 2007|
|Grove-Smith 2015||Grove-Smith J., Krick B., Feist W.: Balancing energy efficiency and renewables, 9th International Conference on Improving Energy Efficiency in Commercial Buildings and Smart Communities, 2015, Conference Proceedings|
|IPCC (2018)||Special Report on 1.5 Degrees Available online: http://www.ipcc.ch/report/sr15/index_background.shtml [Accessed 10th October 2018]|
|Kriesi 1990||Kriesi, Rüdi: Siedlung Boller - Ein Meilenstein des energieeffizienten Bauens; Kanton Zürich, Baudirektion, AWEL Amt für Abfall, Wasser, Energie und Luft|
|Passipedia 2014||Comfort in Passive Houses, Passipedia, Passive House Institute, Darmstadt, 2008-2020|
|PHI 2016||Criteria for the Passive House, EnerPHit and PHI Low Energy BuildingStandard, Passive House Institute, 2016 [Accessed on 28.05.2020]|
|PHPP 2015||W. Feist et al.: PHPP Passive House Planning Package, Version 9 (2015). The energy balance and planning tool for efficient buildings and refurbishments; Passive House Institute; Darmstadt 2015|