Energy Autonomy for Tamera

We’re aiming for 100% energy autonomy for all of Tamera, where 200 people live. This will be a long-term demonstration of a fully autonomous, regenerative and decentralized energy system which can be assembled and maintained on site. We will develop a modular approach which combines many available technologies and which can provide energy autonomy for a typical settlement, including low-infrastructure situations in the Global South or refugee camps.


With this project, we want to create a lived example for our 12 guiding principles:

  • Come together – Community is the basis for sustainability; this supports human communication and allows us to co-exist with nature in a healthy and equitable world which remains in contact with all living beings.
  • Insist on using locally sourced energy – sun, earth, wind, water and biomass.
  • Implement low temperature and low pressure technology for the production of energy.
  • Cooking with solar mirrors and transforming organic waste into biogas integrates humans into a healthy ecological cycle – it therefore is an integral part of an autonomous and holistic approach to food and energy production.
  • Use self-regulating solar energy systems for cooling so that the simplicity of natural energy cycles are incorporated.
  • Cultivate a new paradigm in machinery which mimics the functioning of natural systems as much as possible – for example replacing conventional combustion engines with mechanisms closer to nature such as breathing engines (e.g. the Stirling engine).
  • Integrate energy production into the design of human structures – this means promoting strong synergies between water, ecology, architecture and energy use.
  • Abandon the concept of global, centrally controlled “one way” circuits and move towards decentralized regional circuits that serve local communities.
  • Create open systems which continuously feed energy surplus back into regional grids.
  • Combine systems to eliminate the concept of energy waste – for example energy which heats the biogas digester is also used for thermal storage.
  • Encourage autonomy by supporting local production and focusing on regional resources and communities.
  • Search for continuous improvement through knowledge sharing, open-source systems and continuously returning to the study and observation of nature.
The components of our modular system will include:
  • solar architecture with and without photovoltaic panels,
  • cooking with biogas, direct sunlight and solar-heated hot oil,
  • solar cooling and solar temperature regulation for buildings – with and without seasonal heat storage,
  • solar electric transport,
  • a combined heat and power system run with wood gas and biogas,
  • various regenerative energy technologies for huts and temporary structures.

The energy installations can be installed to provide immediate help in crisis areas and refugee camps, and be instrumental in developing long-term sustainable settlements. Our installations will be used for education. Knowledge transfer starts with us maintaining and living with the systems and then sharing the experience with people coming to learn, so that representatives of other projects can then build and optimize a system that can be integrated into their own daily life.


We’ve developed our energy autonomy concept in collaboration with the Schiller engineering office in Germany.

Elements of the component system:

1. Solar Architecture Combined with Electrical Generation – Photovoltaic Panels and Battery Storage

Our projected electrical energy will be fully covered by photovoltaic panels mounted on the roofs of various buildings. Solar architecture using photovoltaic membrane shade roofs are planned, which will provide a synergy of both shade and electricity, with architecturally and aesthetically appealing structures. The electrical energy generated will be stored in a central battery system for use during the night. We’re looking into alternatives to using lithium batteries, like vanadium redox flow batteries, as they’re not environmentally damaging or dangerous to health, and store electrical energy without loss in physically separated electrolyte tanks. Another option is magnesium-seawater storage, which also doesn’t use any dangerous or toxic materials. Any storage system must have a minimum 20-year lifetime with maximum degradation of 10% of capacity.

2. Solar Cooking: Hot Oil Kitchens, Biogas, Solar Concentrators and Solar Thermal Water Collectors

We want to convert 2 community kitchens to 100% solar energy using hot oil, biogas and solar concentrators. Concentrated vacuum tube solar collectors allow the sun to heat vegetable oil in a closed circuit to a temperature of around 200°C. The hot oil transports heat to double-walled pots and frying pans for cooking and to insulated heat-storage tanks. Biogas is used for cooking at any time of day or night, and Scheffler mirrors concentrate direct solar energy for immediate use. The combination of modules allows 24-hour kitchen operation. Solar thermal hot water collectors heat up the water needed for cooking and cleaning.

3. Solar Energy Generation with Stirling Engine and Thermal Storage

An innovative low-temperature Stirling engine will be installed in Tamera’s Solar Test Field, as the prime mover in an energy supply system providing electricity, cooling, mechanical and heating energy. The selected Stirling engine, SunOrbit’s Sunpulse can deliver 1500W of continuous electrical energy. The engine is a result of decades of research invested by Juergen Kleinwaechter and his team into developing simple and efficient Stirling engines operating in the temperature range delivered by low concentration solar collectors. This system can also be used for cooling by reversing the energy flow and driving the engine with an electrical motor.

We’re developing the elements of a “Hope Container” which is a self-contained energy, food and water management system for 30–50 people. The idea is that they can provide immediate help in crisis areas and refugee camps, and be instrumental in the development of long-term sustainable settlements.

We want to install the basic elements of the “Hope Container” as a prototype in the Solar Test Field and use them for education so that representatives of other projects can learn how to build and optimize a system that can be integrated into their own daily life.

The project has a high synergy with the solar cooking project, in that the same heat collection and storage installation that is used for cooking can also be used with the Stirling engine for electrical power generation.

4. Cooking with Biogas

Both of the larger Tamera kitchens produce abundant biomass in the form of organic waste. This organic waste can easily be processed in small biogas systems by being ground or shredded and used as feedstock in small biogas reactors with a volume up to 10m3. Biogas can be used when the kitchen needs rapid heating, and also when no direct solar heat is available for cooking. The biogas reactors are maintained at an optimal temperature of 37°C with a solar-thermal heating system. The overflow of the slurry is used as biological fertilizer on our fields.

5. Solar Cooling

Using solar energy for cooling is particularly attractive as the need for cooling is highest when the sun is strongest. Control of the cooling system is then almost self-regulating as the heat delivered to the cool room by the sun is counterbalanced by a higher power output from a solar-driven cooling system.

We’re planning to use 3 different solar cooling technologies to provide a range of alternatives for various regions, and we’ll compare them on site to see which performs better:


  • Solar Absorption Coolers
    We’ll install absorption chillers, which have no moving parts, using solar thermal energy from vacuum tube collectors. Absorption chillers work by absorption, performing the condensation phase of the cooling cycle rather than by compression – as usual in a compressor refrigerator. The heat required to regenerate the absorber is readily produced by vacuum tube collectors. The more the sun shines, the more cooling power is available. This is a self-regulating fully CO2-neutral process. The coolant can be ammonia.
  • Reversible Stirling Machine
    The SunOrbit SunPulse can also be driven in reverse, where the Stirling engine is driven electrically and functions as an efficient heat pump/refrigerator. Called a CoolPulse, the process has a COP of 4, significantly higher than conventional refrigeration. For example, when creating ice from water with a starting temperature of 20°C, the CoolPulse operates at a COP of 5. So a typical photovoltaic panel with 500W (peak) electrical energy output can create ice during the day at 2.5kW (peak).We’re planning a test installation with a 2.5kW continuous output. Cooling energy that isn’t needed will be stored in an ice-water storage unit. The photovoltaic panel that drives the installation should have an output power of at least a 3kW peak, so that with a battery bank, it can deliver 500W continuously. The battery should have a storage capacity of 4kWh usable energy.
  • Photovoltaic (PV) Solar Panels with Conventional Refrigeration
    We’ll install a photovoltaic panel and inverter system to drive a conventional compression refrigerator. The cooling energy can also be stored in an ice-water storage system.
6. Wood Gas and Biogas Combined Heat and Power (CHP) System

We need energy sources for electricity and heat when the sun isn’t shining, especially in the winter. We have an abundance of shrubs and bushy plants in Portugal, which are often already dried out by the arid weather. These can be annually harvested, chipped or shredded, and converted to wood gas through a gasification process. This gas is then burned in a wood gas motor and converted into heat and electrical power. The system can be operated economically, complementing the existing solar electricity production to provide a constant electrical energy supply.

The CHP can also be powered with biogas, which has properties similar to wood gas, and the system should produce 10kW of electrical power and 20kW of heat.

We’ll install:

  • – biomass shredder / grinder with sieve
  • – wood chipper
  • – materials handling system to deliver prepared biomass to gasifier
  • – wood gasifier with attached CHP system

Waste heat will be used for water and space heating.

7. Solar Temperature Regulation for Buildings, With and Without Seasonal Heat Storage

In our climate in Portugal, it isn’t possible to live comfortably year-round without heating. We’re planning different demonstration and research temperature regulation systems for buildings. For example: a system of solar thermal collectors mounted on the roofs and connected to a 500L hot water storage tank can heat the walls of buildings. When needed, a secondary heat source such as a wood stove can provide extra heat in the winter months.

For larger structures, an underground seasonal thermal storage tank of 20–200m³ will be installed within the foundations of the buildings to store the heat of the summer to be used in winter. This form of temperature regulation also works to control damp in the building structure.

The storage is made up of gravel and water that’s 2m deep and a heat-exchange tubing. The more water is filled into the gravel substrate, the greater the storage capacity, and the faster the stored heat can be carried into the building through a 1m deep sand or earth buffer in the winter.  The stored heat can also be directly accessed at any time by pumping the warm water through the building’s heating system, which is made up of 3 components:

  • – flat plate collectors on the roof of the building
  • – heating system inside the building
  • – seasonal thermal storage.

In the summer, the excess heat can also be used for cooking, and the hot water used directly. The stored heat can also be used for energy production by driving a Stirling engine.

8. Solar Electric Transport

Introducing solar solutions which demonstrate viable transport alternatives to petroleum-driven combustion engines is key for an energy-autonomous life. It’s particularly important to show practical transport alternatives that don’t need the suggested oil drilling in the region around Portugal‘s coast, to ensure a worthwhile future for local residents.

We’ll install electric vehicle charging stations for electric vehicles, for the transport of both goods and people, that include:

  • – e-bikes
  • – e-scooters
  • – e-cars
  • – golf-carts.

The Smart Grid and Energy Storage Synergy System includes:

  • – 9 electric vehicle charging points
  • – 10 e-cars for on-site use
  • – 2 e-cars for longer journeys.
9. Solar Energy for Huts, Temporary Dwellings and Campsites

In many lower income countries as well as refugee camps, huts, containers and caravan settlements are part of the normal building and living conditions. The caravans and small huts our community members live in are heated with many small, expensive gas bottles. New ways of heating must be implemented.

We’re planning 4 different ways to heat caravans and small huts:


  • Heating with Photovoltaic System, Small Battery Bank and Air Conditioner
    Electrical energy is generated by PV panels on the roof and stored in batteries underneath the caravan. A small air conditioning unit is installed, which can pump both hot and cool air. The more the sun shines, the more cooling energy is available.
  • Solar Thermal Heating System
    Vacuum tube collectors are mounted on caravan roofs, and are connected to heat storage, like hot oil or water storage tanks. This is used in an integrated underfloor heating tube system. Insulation is also added to reduce heat loss. We’re also looking at using the 40°C waste heat from the Sunpulse in the system.
  • Replacing Bottled Gas with Biogas
    We plan to use biogas instead of bottled gas in the existing gas heaters in the caravans and huts. We’ll only have to replace the gas nozzles, and a ring duct will bring biogas from the central biogas reactor, which will be insulated and located close to the caravan settlement. The biogas reactor will be heated in winter to its fermentation temperature of 37°C, either by solar collectors or vacuum tube collectors. The system could also be installed under a construction similar to a greenhouse, which itself reaches a temperature of 37°C relatively easily.
  • Thermal Heating with Biomass         
    We want to use compost piles as water heaters. Compost piles of woodchips and greens filled with water pipes will produce warm water up to 70°C over a period of 6–7 months, supplying a group of caravans with heat for the winter.