Power conservation

With attention being given to rising energy costs, the energy used in an aquarium should be devoted to controlling environmental pollution. Energy is applied primarily for heating, lighting and water treatment.

The following energy considerations are intended to cover a standard aquarium (200 liters) of 100×40x50 cm (L x W x H).

Power consumed: [W] Time [h] energy [kWh / year] Share [%]
Pump 10 24 87.6 14
Heating 33 24 289.1 47
Light 64 10 233.6 38

In total, this makes a yearly consumption of 610 kWh, or about a third of the budget, a single budget being about 1800 kWh. It is therefore quite worthwhile to carry out various ideas on energy conservation.

Energy loss and Heat loss
At 47% of the energy consumed, heating of the aquarium is the most energy-intensive. There are two main factors for this: heat loss by conduction of the glass and heat loss through evaporation.

Regarding heat loss by conduction of the glass, important considerations are the surface that is available for heat exchange, the difference in temperature of the water to the surrounding air, and the heat transfer coefficient, or k-factor. The heat transfer is approximated on the lid and the side walls; the floor is usually somewhat insulated and will be neglected in the analysis. A temperature difference of 5K (25°C water temperature and 20°C is the assumed room temperature) is standard.

Heat loss by conduction:
Material k-factor [W/m2 K] area [m2] Delta T [K] Power [W]
Glass without insulation 7 1.1 5 38.5
Glass with insulation 1 1.1 5 5.5

A high temperature difference as well as a large heat transfer surface area provides for high energy losses.

Heat loss through evaporation:
Evaporation leads to the permanent loss of heat and needs to be tracked. A lighting hood can be installed to substantially reduce air and moisture exchange. The air below the cover becomes saturated with water. When it cannot absorb more moisture, evaporation is suppressed. However, it is not, and should not be, airtight coverage. This will still hold evaporation in check, but to a significantly reduced extent.

The following sample calculation makes this clear. Per square meter of surface, assuming convective air exchange without an aquarium cover, there is a water loss by evaporation of about 5-6 liters per day. With the lid, this is reduced to 1-2 liters per day. At a water temperature of 25°C, about 2441 kJ per kg of water are lost (equivalent to 0.684 kWh per day per liter of water).

Heat loss through evaporation:
Loss (W/m2)
with cover 155
without cover 42

Efficacy
Depending on the bulbs used, the energy is correspondingly affected. Typically the light accounts for 38% of the energy used. The use of LED lights would meet the energy needs in terms of light output while reducing the energy used to about one third. It should be noted, however, that the reduced power consumption of the light is missing as a heat source.

Energy-saving tips
These tips apply to a 200-liter aquarium with 28°C water, fluorescent lights, no cover, and no insulation on top and or sides. They theoretically result in energy savings of around 78%!

Cover the aquarium, which possibly also controls evaporation.

Isolate the aquarium sides and lid with Styrofoam plates, possibly also with interior decoration walls.

Adjust lighting to LED technology, possibly reducing lighting time.

Reduce water temperature; usually fish live at slightly lower temperatures in their natural habitat. For example, instead of 28°C, set the temperature at 25°C.

Replace an external pump with an internal pump. On the one hand, there is no heat loss through the pipes and the filter, on the other is the power dissipation of the electric motor. The benefit is the thermal balance of the water. Water hoses may be isolated.

In new construction, provide the vision panels with insulated glass.