A reliable source of energy is critical for social development and poverty reduction. Our target appropriate energy technologies for the campus are a low-head microhydrelectric power plant, and a methane biodigestor.
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. An important part of 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. 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. More information about these energy projects is given below.
Gravitational vortex hydropower (GVHP) 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 the campus.
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. 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.
The rotation tank and water channels were contructed from reinforced concrete, with a specific design that induces vortex formation in the tank. Various gates and grates at the river and tank inlet are used to control the water flow and prevent debris entering the system. The water flows through the plant and then returns downstream to the river.
The water enters the tank of the GVHP system and forms a vortex. The turbine is placed within the core of the vortex, and converts the kinetic energy to electricity via a transmission system and a generator.
This project was started in 2015 and gave its first power in 2016. In 2017 we upgraded the system to give more power, and identified that the power transmission is a limitation of this system. The slow rotation speed of the turbine results in very high torque, which is a challenging condition for traditional gearboxes. Industrial gearboxes designed for use in heavy machinery only operate several hours per day. However, in the case of the hydroelectric plant running 24 hours a day, such gearboxes will only last a few years before needing to be replaced. Hence, we spent several years investigating magnetic gearboxes for more reliable and low-maintenance performance. Magnetic gearboxes are a new technology that has no contacting parts, no need for lubrication, and automatic overload protection when the designed torque is exceeded. However, after several generations of gearbox prototypes, we concluded that this technology is not a suitable appropriate technology for combination with the GVHP as it requires a high level of precise machining that makes construction and installation difficult. Our new strategy is to increase the speed of the turbine to reduce the torque, allowing the use of commercially available gearboxes. First testing of this system in early 2020 has shown promising results.
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.
”Design and construction of an off-grid gravitational vortex hydropower plant: A case study in rural Peru” Alzamora Guzmán et al., Sustainable Energy Technologies and Assessments 35 (2019) 131–138
Methane digester for biogas production
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. The methane-rich gas generated by this process can be cleaned and then used for cooking, heating, or electricity production. 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 residue can be further treated using fermentation and oxygenation processes to produce biols, which are biologically active solutions that can be used as nutrient-rich fertilizers, foliar sprays for pest and disease control in plants, and soil enrichment, among other applications.
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 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. Naturally occurring biogas produced in soil and compost heaps is 30-40% methane, while gas from a digester is usually 60-70% methane. The methane-rich gas needs to be fed through a gas cleaning system to remove hydrogen sulfide and other contaminants, to make it safe for storage and use.
The biogas project is being developed in collaboration with the Universidad Nacional Agraria La Molina. Small-scale biological experiments will be performed in the university to select appropriate organisms for the fermentation reactions, which will then be used to innocculate the full-scale system at Kadagaya. Installation of the infrastructure for the biogas tank and associated sanitation systems was begun in early 2020.