Vortex hydroelectric plant: Nearing completion (2019)

Biogas: Research phase (inactive)

In the developed world energy abundance is achieved through the consumption of cheap, high-energy fossil fuels such as coal, oil and gas. These non-renewable energy sources have improved the living standards of millions of people, but their rapid exploitation has had adverse effects on the planet. In addition, the inequitable access to energy worldwide has created political and social stresses resulting from an economic dependence on oil-producing regions. Future energy systems need to provide energy abundance while being sustainable and non-polluting. Energy production should be distributed, diverse, intelligent, and highly integrated into technological, industrial, and domestic systems. At Kadagaya, we evaluate energy systems based on their ability to efficiently and cleanly provide abundant energy, where open-source designs are preferred in order to provide equitable access. Energy is intrinsically linked to all systems (housing, agriculture, water and waste treatment, industry, and transport). Hence, energy production, monitoring, efficiency, and use need to be carefully considered during the design stage. The ideal scenario for a self-sufficient community is to produce as much energy as possible from waste products (human waste, food waste, waste heat), i.e. “energy recycling” and the renewable sources available at the location (e.g. solar, wind, hydro).  We evaluated various energy technologies with respect to the type of generation (base-load or variable), reliability, lifetime, cost per kWh of energy generated, ongoing costs of maintenance and consumables, whether open-source designs are available, and the impact of the manufacture (energy use, environmental problems).

At the Kadagaya campus, we are focusing on two main energy sources (hydroelectricity and biogas). Wind energy is not viable at our present location and small installations are expensive for the amount of power they produce. Solar power has inherent dependence on the market for purchase of the panels and a large amount of storage (via batteries) is required as energy generation is only during the day. The cost of photovoltaic panels continues to rapidly decrease and now the major cost over the lifetime of the system is the batteries (which have a much shorter life than the panels). Our electrical power is supplied by a vortex hydroelectric power plant on our river. This technology was selected as it can supply high amounts of energy continuously with little maintenance. This project was started in 2015 and gave its first power in 2016. In 2017 we upgraded the system to give more power, which led to side project of developing magnetic gearboxes for more reliable and low-maintenance performance. We hope to have the new and improved system back online in the first half of 2019.

In addition to electricity, the other important energy source for cooking and heating is gas. This can be obtained using a biodigester system where methane (“biogas”) can be produced from organic (human, animal and agricultural) wastes. This project is still in the design phase and requires much more infrastructure to be installed before we can start this project. An important part of remote, off-grid, and self-sufficient living is incorporating back-up systems. Currently, we have a small solar photovoltaic system, a petrol generator, and access to the electrical grid as back-up power systems. In the future, we plant to use pumped hydro as a back-up “battery” when the vortex hydroelectric plant needs to be shut down for maintenance. 

Vortex hydroelectric system

This technology was selected as it is cost effective, generates power all year round (24 hours a day), with no required storage, and can easily provide enough power for our requirements. Excess power can be provided to our neighbours and converted into income-generating projects. Usually hydroelectric systems require a high head (drop in altitude) to produce sufficient electricity. For example, Pelton systems use a rapidly-rotating propeller fed by water falling from a waterfall or down a mountainside. Large-scale industrial hydroelectric plants need to build enormous dams to provide this head and control the water flow (which can be very damaging to the ecosystem). The vortex system is suitable for a river such as ours with low head and high flow. The water is fed into a tank with a geometry that causes the water to rotate in a vortex, which spins a vertical axis turbine that harnesses the kinetic energy, while an attached generator converts it into electricity. We consider this an appropriate technology as it is a very simple system that can be constructed in remote locations with the resources available in remote areas of developing countries. In addition, it has a positive effect on the local ecosystem (the vortex aerates the water and allows the passing of fish in both directions), while all water is returned to the river where it continues with its natural flow rate.

We are using a relatively small vortex system, with a 5 m diameter tank and a head around 1 m, which enables us to generate 5 – 10 kW every hour, or 120 - 240 kWh/day. An average (developed world) household uses about 10 kWh/day, so such a system can easily supply the needs of a small community. Many of the technical details of this project have been documented and we are very happy to share all of our knoweldge and experience. If you would like more information, please contact us. Videos of the system operating can be found at our Youtube channel

Methane digester for biogas

Digesters mimic the natural decomposition process occurring in soils, where the waste is processed by a complex biota of bacteria and fungi. Natural composting is a slow process and requires a lot of land. Natural degradation produces methane, which is a strongly active greenhouse gas, so it is preferable that these reactions occur in a controlled environment where the methane can be captured and used. Biodigester systems are simply tanks filled with organic waste, which are controlled to optimise the decomposition reaction to both sanitise the waste and produce methane. The remaining solid residue is a nutrient-rich fertilizer.

We have outlined a preliminary plan for our biodigester system considering the needs of the future buildings and the natural slope of the site. The system will probably be operated in “co-digestion” mode, where the reactor will be fed with a mixture of different wastes. In addition to human waste, residues from agriculture could be used to give better gas yields and compost with higher levels of nutrients. We plan to design a high-temperature system (operating around 70 °C), which offers several advantages. Only “thermophilic” bacteria, which can tolerate this temperature, are active, and no pathogenic bacteria survive. When the sludge is cooled for removal, the thermophilic bacteria die and the sterile sludge can be immediately used. In addition, the high-temperature process has a higher reaction rate, better gas yields, and can be more easily controlled than lower-temperature processes. Naturally occurring biogas produced in soil and compost heaps is 30-40% methane, while gas from a digester is usually 60-70% methane.

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