on site solar & water

 

The solar hot water unit on this house was originally functional. It became useless and was removed after fast growing trees overshadowed the roof

Annual daily irradiation on an inclined plane expressed as % of maximum (Sydney) 

 

Reed beds under construction. Purpose made tanks are now made by Duraplas.

 

 Naturalistic reed beds and settling pond

Owner built council approved compost toilet. Commercial models, e.g. Clivus Mulstrum are available

solar power

How big?  Sizing of a photovoltaic (PV) system depends on household power consumption, whether the system is stand alone or grid connected, budget, potential future system expansion and the current situation with rebates. We leave this part to specialists like Solar Inverters (www.solarinverters.com.au) or Self sufficient Homes (www.selfsufficienthomes.com.au).

Enough sun?  Planning for PV should include a survey of the existing vegetation and an estimate of future tree overshadowing. Trees can grow fast in our area (NSW mid north coast) and issues have arisen with loss of PV productivity some years after installation due to the rapid growth of trees beyond the property boundary. The specialists can also run a light test to estimate present day solar access viability.

How much space?   15-30 square metres is the minimum area of north facing roof space required for a 1.6- 3kW system. An additional allowance may be required to accomodate the PV panel shape. Ideally, a house will be oriented north with plenty of north facing roof, however in some cases it is necessary to design a small section of roof or carport specifically oriented for solar power.

Ideal orientation & angle?  See the table opposite adapted from the Clean Energy Council (www.cleanenergycouncil.org.au) recommendations:

solar hot water

Similarities exist with solar power. We design for solar hot water by considering roof position, future overshadowing and an allowance for the weight of a rooftop solar hot water tank. Government subsidies can be prone to change so consult specialists for the system requirements and the latest prices.

 on site water

How big?  Relatively small tanks will provide most of water requirements for a household most of the time. For example, Southern Cross University ran computer modelling for water tank sizes based on rainfall in Lismore over the past 25 years, for a 3 person household (using 120L/day each) and 180 square metres of roof. The modelling suggested that a 45,000 L tank would supply the full water demand, but only a 4,200L tank would supply 80% of the water over that time.

Pumps  Design should avoid pump noise irritating the occupants or neighbours. 

on site water treatment

Compost toilets  We like composting toilets because they don't use water. This saves water and keeps faecies out of the water stream, making on site treatment easier and more compact. If properly managed, the compost can be used as a fertilizer, keeping precious nutrient on site.

Reed beds  While streams and rivers need nutrient for life, excess nutrient is the enemy of natural waterways, producing algal blooms which starve the water of dissolved oxygen. On site water treatment is about consuming nutrient before it leaves the site. Reedbeds are a nice, low tech way of doing this. Surprisingly, it is not so much the plants that consume nutrient, but the bacteria living around the plant roots and substrate. Reed beds are often used where a higher level of treatment is required than septic + evapotranspitration trenches (gravel beds surrounded by vegetation), or where there is insufficient space for evapotranspiration trenches.

AWTS (Aerated Wastewater Treatment Systems)  look like an in ground water tank. They filter, settle and stir water, some even use chlorine or UV lamps to achieve very high treatment levels. They are compact and can do the job but are relatively high tech and usually come with costly maintenance contracts.

What do we do? 

Assuming a new building, we consider your on site resource management in the beginning and help work out the best options. We design for it by allowing space, solar access and aesthetic arrangement. We work with specialists on some of the detail, for example reed bed sizes or cost comparisons.