Renewable Energy Water Heating Technologies

Solar water heaters

A solar water heater or heat pump can help reduce your energy usage over time and bring your carbon emissions down too. Solar roof systems for hot water are now very common. Estimate the roof area required for a large solar hot water system:

  • Estimate the hot water load (GJ) with an assumed daily load
  • Determine average solar daily solar radiation for the location (for example Melbourne, Australia is ~ 15 JM/m2d
  • Assume solar collection efficiency ~ 0.35
  • Assume utilization efficiency ~0.7

Load = Solar Radiation * Collector Area * Collection Efficiency * Utilisation Efficiency


Solar Hot Water

Solar Hot Water

Biomass water heaters 

Types of Biomass

Types of Biomass

Biomass heating systems generate heat from biomass (biological material such as wood, plant materials or animal matter). As an energy source , biomass can be used directly via combustion to produce heat, or indirectly after converting it to various forms of biofuel. The systems fall under the categories of:

  • direct combustion
  • gasification
  • combined heat and power
  • anaerobic digestion
  • aerobic digestion

Benefits from biomass heating is the lower impact on the environment. Drawbacks include greater air pollutants and carbon in the atmosphere if used on a large scale through combustion of biomass. The use of biomass takes agricultural land out of food production, reduces the carbon sequestration capacity of forests, and extracts nutrients from the soil.

The use of Biomass in heating systems has a use in many different types of buildings, and all have different uses. There are four main types of heating systems that use biomass to heat a boiler. The types are Fully Automated, Semi-Automated, Pellet-Fired, and Combined Heat and Power.

Fully automatedChipped or ground up waste wood is brought to the site by delivery trucks and dropped into a holding tank. A system of conveyors then transports the wood from the holding tank to the boiler at a certain managed rate. This rate is managed by computer controls and a laser that measures the load of fuel the conveyor is bringing in. The system automatically goes on and off to maintain the pressure and temperature within the boiler.

Types of Biomass Pellets

Types of Biomass Pellets – Fuel Types

Semi-automated or “surge bin”: Same as fully automated systems but requires more manpower to keep operational, and therefore cheaper.

Pellet-fired: Pellets are a processed form of wood, which make them more expensive. Although they are more expensive, they are much more condensed and uniform, and therefore are more efficient. In these systems, the pellets are stored in a grain-type storage silo, and gravity is used to move them to the boiler. The storage requirements are much smaller for pellet-fired systems because of their condensed nature, which also helps cut down costs.

Agricultural pellet systems: Sub category of pellet systems are boilers or burners capable of burning pellet with higher ash rate (paper pellets, hay pellets, straw pellets). In terms of efficiencies advanced pellet boilers can exceed other forms of biomass because of the more stable fuel characteristics. Advanced pellet boilers can even work in condensing mode and cool down combustion gases to 30-40°C, instead of 120°C before sent into the flue.

Combined heat and power: Generate power, and heat is created as a byproduct of the power generation system. They have a very high cost because of the high pressure operation.


Geothermal heating and cooling systems

Geothermal heating and cooling systems that tap into the constant temperature of the shallow ground to create the most energy-efficient climate control systems for air conditioning, hot water services, hydronic floor heating, radiator wall panels, swimming pools & spas.

Geothermal heat pumps, also known as ground source heat pumps (GSHPs), are used to transfer natural heat from shallow earth to the inside of a building delivering energy-efficient space and/or water heating. The same principle is used in reverse to cool the air inside a building, by transferring the heat from the building into the shallow earth below.

A typical Direct Geothermal system comprises a heat pump, ground loop and a heat distribution system such as a forced air conditioner, radiators or under floor heating. The ground loop is a series of closed loop pipes buried in a bore-hole or a horizontal trench through which water is carried. In heating mode, water is pumped through the ground loop to extract heat from the ground. The heat pump then transfers heat into the building through a traditional air conditioning unit or water heating unit delivering energy-saving space heating and water heating. In cooling mode, the heat pump acts to remove the heat from the building and to transfer it to the earth using this same principle in reverse.

Geothermal water heating

Geothermal water heating


Geothermal Heating and Cooling System Schematic

Geothermal Heating and Cooling System Schematic

Geothermal heating and cooling systems

Geothermal heating and cooling systems


Source: Geothermal heating and cooling; Wikipedia,

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