How do you design a sustainable water strategy for an elephant? And how many of us ever get the chance, especially in the UK? But that’s exactly what the Skanda Vale community in Carmarthen did recently for their adopted elephant Valli. Her living quarters needed updating and this has been done with the emphasis on thermal performance of the building fabric (though when you need a door big enough for an elephant to be permanently open during daylight hours, there is obviously only so much that can be achieved). The building design aimed to combine spacious, stimulating accommodation for elephants, with an efficient zero-carbon heating and hot water system. The total floor area is 440 m2, and the building is 8m high. Valli’s accommodation occupies the full height of over three quarters of the floor area. The remainder is taken up with a two storey annexe, under the same roof, behind the elephant area, which includes an office, staff room, shower and toilet, hay storage area, and observation gallery. There is also an in-house boiler room and wood store.
However, it is the water side of things that is very different to most buildings. Valli has an indoor plunge pool and waterfall available to her. The pool holds 12,000 litres (12m3) of water. If Valli lies down in the pool, she can displace a tonne of water (1,000 litres) – so good drainage is essential (though not all this water runs to waste). Top up is infrequent and is probably less than 500l a week. Every few months the water is changed completely.
Brother Stefan, one of the main carers of Valli, designed the pipe work for the waterfall. The filtration system for the pool is, in effect, a small sewage treatment plant. Plastic bio balls are housed in a 300mm diameter pipe to create an extensive surface for aerobic bacteria to colonise. These bacteria break down organic matter (such as elephant poo!) in the recirculated water.
The main interior wall is concrete with an in-wall heating system. Underfloor heating pipe was laid 30mm deep, at 100mm spacing, within the concrete layer. It is fed with warm water between 45 to 50 degrees C and creates a 3.7m high, 22m long source of radiant heat, which Valli can stand beside or lean against to warm herself on cool days, even with the door to her enclosure open. The heated wall provides a highly energy efficient way to create micro climates of hot and cold areas within the building. When the door is closed, the well-insulated roof (overall U value of 0.2) and walls (U-value 0.23) combined with double glazed windows, means the building can be economically maintained at a temperature of 16 degrees C whatever the weather outside. In the ten months since the building was opened (December 2013) 12,000 kWh of heat has been used (against a total yearly estimate of 23,000 kWh). Whilst the winter of 2013/14 was warm (if very wet!), a lot of extra heat was required in the first four weeks to dry the sand that covers most of the floor area. An additional source of heating is Valli herself – elephants emit an average of 2.5 kW, theoretically reducing the annual heating requirement by around 11,000kWh (8,640 hours by 2.5 kW is 21,500 kWh but the heat is useless in summer!) Over the 6 to 7 months that heating is required about 11 – 13,000 kWh is generated by one elephant. About 3000 kWh is required for hot water.
The zero-carbon heating and hot water system combines a 30 kW log boiler and a 9kW south facing solar thermal array. It is calculated (based on the performance of their 6 kW array which has just been increased in size) that the new array will contributes 5,500 kWh of hot water a year, used for space heating as well as hot water. Valli has a daily ‘bath’ when she is hosed down over a specially designed area floored with a soft layer of recycled tyres. Hot water (up to 40 degrees C) is required for this, apart from hot summer days when she will have a cold one. There is also a shower room for human use only. The solar panels and the log burner are connected to a 2,500 litre accumulator tank. Cold water is heated instantaneously as it passes through the accumulator (via a flat, spiralling stainless steel pipe with a surface area of 7.8m2). With no store of domestic hot water, there is no requirement to heat the water to 60 degrees C to prevent legionella proliferation, and so no back up to the solar thermal system is required when the boiler is not on. As this would have been an electric immersion heater, it makes the hot water supply very carbon efficient. On average this summer the system has been providing hot water at 45 degrees C, more than adequate for an elephant hose down!
The community had considered photovoltaic panels, but Valli’s house needs heat and hot water, rather than electricity. Although there are lights both internal and external, they are highly efficient 10 Watt LED units, and only used during the hours of darkness. Electricity from PV panels has to be stored in batteries (with all the environmental disadvantages that entails), whereas it is easy to store hot water. The total cost of the solar thermal system was £3,750, and with a life expectancy of 20 years that works out at 3.4p/kWh. It also qualifies for an RHI payment of £550 a year for 20 years.
Water use will be continually reviewed. Future plans include the installation of a 10,000 litre rainwater harvesting tank, fed from the roof of the elephant house, to supplement the water currently coming from the monastery borehole. The rainwater will be used to fill up Valli’s pool as well as the duck ponds on the adjacent field.
Sally Hall
This is a water focused version of an original article from Green Building magazine, Autumn 2014
Posted April 2015