How did I not find this thread sooner??? Yona, thank you for a magnificent question!
What sort of grand-scale research needs to be done in the permaculture community?
Here's a few things high on my list if I ever find myself with more time than stuff to do... Some are research in the science sense, and some or more about engineering guidelines, but both are directly useful for projects in my future.
Test the effects of waterproof umbrella with and without insulation on soil temperature vs. depth. My intention here is directly related to wofati design, but it's useful information for other earth sheltered buildings, and even for conventional buildings with horizontal insulation around their foundation.
The experimental setup would be a series of shafts drilled 12 - 20 feet deep. Each shaft has a set of temperature sensors lowered in, positioned perhaps a foot apart, then the shaft is backfilled. All sensors for all shafts would be connected to a data logger, as would one more sensor which detects ambient air temperature.One shaft would be the control, having the sensors as described above and no other treatment. The hypothesis is that temperature in this shaft will follow change in ambient air temperature, but as we go deeper the temperature swings less and the time lag from surface change is longer.A second shaft would have an umbrella over it, wofati style, spread perhaps 10 to 20 feet to each side of the shaft. The hypothesis is that the temperature swings observed in this shaft will occur slower than the control, especially when there is precipitation which wets the soil and speeds the temperature change in the control. Perhaps adding soil moisture sensors to both shafts would also be useful.A third shaft would have an umbrella over it, then an insulation layer, and then another umbrella to keep the insulation dry... exactly like a wofati. The hypothesis is that temperature swings observed in this shaft will occur much slower than either prior shaft.Additional shafts could be used with different insulation amounts, thereby determining the amount of insulation necessary to stabilize the temperature within a desired range, given a specified depth.
Test a freezer wofati
As long as we're looking at wofati related things, I believe Paul is still keen to build and test a freezer wofati.
Threads elsewhere on this site explain that.
Rocket Mass Heater related research
Measure temperatures in various parts of a RMH J-tube, exploring various design/size options and how they impact temperature distribution.Measure combustion efficiency from a RMH, as measured by exit gasses (as Peter V has done in recent innovator's events), and tweak both J-tube and batch box designs to explore the factors that affect the efficiency.
Various building materials experiments...
Experiment with various aircrete mixes, standardizing ingredients and process to produce them, and publish data on compressive strength, tensile strength (very low), density, etc.Experiment with aircrete mixes with specifically avoid portland cement, determining which alternative materials (pozzalans, MgO solutions, etc) are viable, and publishing needed data for mix design and strength.Determine whether straw bale insulation is viable below grade, if adequately waterproofed. Explanation... Mike Oeler's & Paul Wheaton argue that a wood pole foundation will not rot quickly, as long as it's kept dry. If correct, this seems to eliminate the principal concern with using strawbales for sub-grade insulation... so bury straw bales that are waterproofed with a reasonable DIY natural building technique, perhaps plastering them, then putting a wofati style umbrella over them... then dig them up years later and measure if and how much degradation or decay has occurred.
There are soooo many different arguments about composting toilet designs. In the humanure handbook, Jenkins publishes many years of very useful data, but many people have fecophobia and don't want to use the bucket system. So, we need a side by side comparison of the many other systems vying for this space... Paul Wheaton's willow feeders, clivus multrum, worm based systems, etc. I believe that Paul and Fred might have strongly different opinions in this area and it could be fun to engage them and learn from both.
I'd love to measure the efficiency of various collectors (either solar water or solar air heating), but not the thermal efficiency (output energy / input sunlight) because that's not critical when the input energy is free. Rather, I'd like to measure their economic efficiency (output energy / input $ to construct). Test results of the economic efficiency of various standard collector designs could be very useful for DIYers and permies everywhere.
And if we really want to get wild, research the potential for homestead scale power generation with ringbom stirling engines powered by the temperature differential between stable earth temperature and atmospheric temperature.
That one probably demands a little explanation...
Stirling engines are external combustion engines. They don't burn fuel internally, they operate from the temperature differential between a hot side and a cool side. For example, you could focus a concentrating solar collector on the hot side of a stirling engine and it will go.There is a class of stirling engines, known as ringbom stirling engines, which is specifically designed to run on very low temperature differentials, sometimes less than ten degrees.Such a temperature differential could easily be provided by the difference between deep earth temperature (12 to 20 feet is enough to be reasonably stable), and atmospheric temperature during the high and low temperature parts of the day.Research area #1 - for a given climate area, examine the theoretical power available from the ground to air temperature differential, based on historic temperature swings vs time of year. Consider the size of heat exchanger needed in the ground to ensure the power generated doesn't cease due to local ground heating or cooling faster than the temperature change can be dissipated within the surrounding earth. Consider the size of atmospheric heat exchanger needed and viable technologies for it. Based on these heat exchanger sizes and costs, is the theoretically available power economically feasible?Note - the efficiency of stirling engines is very close to the carnot cycle, meaning that their efficiency is proportional to the magnitude of the difference between the hot side temperature and the cold side. This means that ringbom stirling engines, being designed to operate on low temperature differentials, are fundamentally designed to be highly inefficient. At one level this is irrelevant if the input energy is free, but that doesn't mean it's economically a good idea.Research area #2 - if the theoretical numbers work, then design and test solutions to actually do this.
There's tons of research opportunities around various geothermal heating/cooling solutions for DIY/natural building...
The WOFATI is one example.
People operating greenhouses which circulate their air through systems of pipes beneath the greenhouse are another example.
And this list is just getting warmed up... there's so much more...