The art of integrative design
Last week, I had the chance to listen to Amory B Lovins, as he was giving a presentation at the climate-KIC green garage about his concept of integrative design. For those, who have not heard of him yet, check out this comprehensive session on savings through integrative design.
The concept of integrative design
The key of his concept is to look at the entire system to achieve the highest overall savings, instead of just picking one or two improvements. Too make this concept works, he factors in the avoided cost of elements that can entirely avoided by spending more on others.
One of the examples he used in his presentation was to insulate his home so much, that no heating system is required anymore. The saved costs through energy savings in addition with the avoided costs for the heating system would make up for the additional cost of insulation material. Overall this results in a faster payback, as much higher savings can be achieved.
Another example is when laying out piping systems to start with the pipes first and then include the pumps. Also here, making the pipes have a bigger diameter and leaving out rectangular turns (that create friction) requires more material and thus higher cost initially. But through the bigger diameter and optimized flow, less energy for pumping is required. This results in overall much higher operational savings, of up to 90% on traditional layouts, offsetting the initial additional cost significantly faster.
Traditional design for off-grid systems
So what does this mean for off-grid systems?
When designing greenfield systems, typically the diesel generator plant to supply the energy is designed based on the estimated (or given) number of appliances, their time of usage during the day, and their specific power rating. Based on this, and with some operational parameters such as n+1 criteria and operational margins for spinning reserve and operational reserve the number of generators and their size are selected.
Now here is the thing: If someone were to ask for a solar/battery based comparable system to the diesel generator one, he would say “we need X kW of power, with a 100% backup capability and 24/7 supply, as the diesel plant can supply”.
And then a comparison is done between the two. But often, this comparison is not truly comparable. Why? Because it lacks the integrative approach. A proper comparison of the two would mean to compare both, with all of their cost elements. This means to include capex of the power house building, the fuel tanks, the diesel fuel pumps, the pipe works, all of the diesel related things. Yet, I have never come across such a comparison. Usually, the movable assets are being compared to each other.
And the same applies for the overall lifetime cost. Often, in the comparison between the two cases the cost of PV and battery maintenance is added up onto the diesel maintenance and plant operator cost. This blows up the PV/battery case compared to the diesel only case. This comes as the assumption is made that a diesel generator is still required. The approach of integrative design here would mean, to size the solar/battery system so that the diesel generator and all related elements could completely be left out. Only then, much more efficient systems can be achieved as a lot of operational cost can be left out, resulting in a faster payback, especially when all capex elements solely for the diesel infrastructure can be left out.
Limitations when retrofitting existing systems?
Currently there is a big hype in the market for retrofitting existing diesel based systems with solar PV – the so called solar/diesel hybrid systems. Core concept is to keep the capital expenditure low, as no storage is required and easy integration with hybrid controllers is possible that maintain a stable grid.
However, again, this approach for brown field projects does not look at the overall system. It leaves out saving potentials. For example many off-grid system users (e.g. tourism lodges) have diesel boilers for hot water. When thinking integrative, these could be switched over to electrical boilers. Initially one could think this would leave to higher consumption of diesel. Due to the smaller efficiency of the electrical boilers and their power demand added up to the already existing demand. But yet, when looked at this from an integrative approach, it means that when replacing the diesel engines with a solar/battery system, suddenly the battery capacity could be smaller. This comes as one can utilize the electrical boilers as deferrable loads, and their hot water tanks as energy storage devices. As always, when applying integrative design, it means that these improvements come in loops. Once the initial integration of an element is done, this has impact on others. A good analogy here is the car: When building electric cars, making them lighter results in less energy required to move them. This allows for less storage capacity in batteries. Which then results in less weight of the batteries, allowing for the underlying structure to be made smaller and thus less heavy. This goes on and on.
Albeit this is just an example, I am sure there are many more to find that altogether provide a much more integrated and hence a much more efficient solution. I am thinking of energy saving consumers (e.g. LED bulbs), timer switches, deferrable pumping loads and so on.
What can we learn from integrative design?
One thing Amory pointed out during his talk was the following: “The most optimal systems are shown to mankind by nature. And nature does not compromise, it ultimately optimises. The Pelican is the most optimum Pelican in the world, as nature had thousands of years to optimise it, with every cycle of evolution.”
So maybe, when we try to find the optimum for a diesel based off-grid system, we should think more outside of the box to achieve less diesel consumption. We have to find these components that are left out in the traditional design process of hybrid systems. And we need to integrate them in our design. To find the optimum, not a compromise.