Energy Redundancy
Energy redundancy for cooking, washing and lighting is essential in a remote area subject to weather extremes so all household necessities are backed up with alternate sources namely gas, wood, kerosene and electricity via mains power or petrol generator. Our power board can switch from mains to generator power with the manual flip of a switch.
The multifunction wood stove reduces our carbon footprint while supplying most of our dehumidifying, water heating and cooking energy needs. Our wood supply results from our rainforest restoration activities. Tea plants from nearby tea plantations have invaded the rainforest margins and grown into tree size. We selectively harvest these and replace them with rainforest native fruit bearing plants we find germinating in cassowary scats (cassowary poo!). We keep comfortable and the cassowary gets a bigger source of its favourite fruits! Our woodstove has an integral hot water tank which is connected via a thermosiphon to a large insulated conventional hot water storage tank. The hot water storage tank has its own electrical element so it can heat water independent of the woodstove. the hot water storage tank is also cnnected to the output of an on demand gas water heater. The on-demand gas water heated may be used independently or it can receive "pre-heated" water from the storage tank (thus reducing gas consumption. A normal 45kg cylinder of gas lasts anywhere from 6 to 9 months and there is a second redundant gas cylinder when the first runs out. In various combinations this system facilitates a range of uses namely:
for small batches of hot water the on-demand gas water heater may be used independently or with reduced running costs using "pre-heated" hot woodstove water from the storage tank
for larger batches of hot water the on-demand gas heater can be disconnected and "free" hotwater obtained from the woodstove connected hot water storage tank - alternatively you could use electricity to heat the storage tank water in the storage tank on days when you do not want to light the woodstove but have a high hot water demand
the woodstove heats water, the hot "expanded" water siphons into the hot water storage tank and cool water from the storage tank siphons back into the woodstove. - this is called a "thermo-siphon" -when the woodstove cools you can close the valves between the woodstove and the storage tank and have a couple of days stored supply of household hot water
when the woodstove cools down the flow in the "thermo-siphon" is reversed, hot water enters the woodstove tank where it is cooled and returns to the storage tank - close the damper and the woodstove becomes a "radiant heater" - as a result you can run a fire for a period then extend that heating of the house with hot water
the woodstove has an oven and a cooktop and may be used for cooking and baking
the woodstove works as an effective dehumidifier
so in summary by the simple manipulation of valves you have ---> a gas water heater, -->a gas water heater supplimented with hot woodstove water, -->a gas water heater supplimented with electrically heated water,--> woodstove hot water, -->electrically heated water, -->a radiant heater, --> cooking and baking, --> as a dehumidifier
The wood supply is sustainable. As fast as we cut the tea plants down they regrow from the base. The tea trees are large enough to harvest again after about 7 years and their high tannic acid content protects them from insects over the year they take to dry before use. We light about 100 fires a year in the wood stove for water heating, cooking and dehumidifying. Each use averages about 3kg of dry wood so 300kg of dry wood per year. Each tea plant gives us about 3kg wet and 2kg dry of wood so 300kg per year / 2kg yields about 150 tea plants. The tea infestation covers about an 3000sqm with about 1500 plants / 150plants per year equals 10 years supply years supply. We use smaller diameter timber, about the diameter of an arm . It dries uniformly, can be cut to a uniform lenght using an electric mitre saw and requires little or no splitting. As we carry out rainforest restoration we keep the current canopy largely intact, selectively intersperse tea and natives in cleared open patches and restablish the canopy with native trees.
Our wood supply will reduce in area over the years but will still meet our needs. The stainless steel flue, exposed internally from wood stove to ceiling acts as a giant gentle 5m+ long radiator. Under the rainforest canopy the air is often dead still so it is important to get the woodstove burning and drawing well before adjusting airflow.
I prefer to cut the tea trees down with an axe and use a controlled drop plants with minimal damage to surrounding natives. My experience is that when a chainsaw is used it can to a lot of damage in a sensitive area. A sliding mitre saw is used to size firewood yielding uniform size logs quickly and safely. The same saw is used to create bookshelf walls and dividers made from rainforest timber rescued during site clearance.
Generally in the tropics building materials with low thermal mass are favoured in construction. Selective use of thermal mass, however, can be useful in the rainforest due to the unique microclimate created by massive volumes of evaporation and transpiration. Heat is vented from the jungle via this natural heat pump resulting in notably cooler temperatures under the canopy. This is natural heat pump is exploited favourably in our design. The thermally massive shaded pods supporting Studio Nimbus store this “coolth” which is productively released during the heat of the day into the lower balcony roofs and under the main floor. The cooled air is then drawn passively through the house. Thermal mass for the most part works in our favour but there are times when it does not. About 3 or 4 times a year a period of cool dry weather is quickly followed by warm moist weather. At these times we can get condensation on the balcony tiled floors. The interior of the pods is unaffected provided we keep the doors and windows shut for a few hours. The trade-off is worthwhile for the vast majority of the year.
