Getting ready to go off the grid

Suppose you have a solar photovoltaic system or a BlueGen fuel cell home generator and a collection of appliances that can be monitored and controlled automatically by a tablet computer.

A hot water system might be set to keep water between 50°C and 60°C.

• If the water temperature is at or below 50°C, the water heater should be on. 
• If the water temperature is at or above 60°C the water heater should be off.

When the water temperature is anywhere between these upper and lower temperatures the status of the heater could be on or off. From your point of view, the status of the water heater ("on" or "off") is "Don't care if on or off".

Refrigerators, freezers, air-conditioners and space heaters can be automatically controlled having regard to:

• A lower temperature at which the appliance should be "on" (for heating appliances) and "off" (for cooling appliances)
• An upper temperature at which the appliance should be "off" (for heating appliances) and "on" (for cooling appliances) 
• For any temperature that is between the lower and upper temperature, the appliance has a status of "Don't care if on or off".

When your home energy system is generating more energy than is required for all appliances that are turned on, extra energy can be sent to some or all appliances that are "off" but have a status of "Don't care if on or off".

A ZigBee HVAC Application

When your home energy system is not generating enough energy for all appliances that are turned on, energy can be saved by cutting energy being sent to some or all appliances that are "on" but have a status of "Don't care if on or off".

Controlling appliances in this way reduces the size and cost of energy storage.

• Excess energy being generated is added to any appliance that can use it.
• Peak energy use is lowered - when more energy is being used than is being generating - by automatically withholding supply from any appliance that can postpone its energy needs.

If your household has an electric vehicle parked in a garage, it can be controlled in an even better way. For example:

• When the battery charge is below 40 percent, charging should be "on".
• When the battery charge is at 100 percent, charging should be "off".
• When the battery charge is between 40 percent and 80 percent, charging can be considered to be "Don't care if on or off".
• When the battery charge is between 80 percent and 100 percent, the battery can be considered to be "Don't care if charging is on or off, OR if discharging is on or off". (That is to optionally SUPPLY energy to the home.)

Notice that the last status above allows the household to make use of any electric vehicle parked in its garage for energy storage - at no extra cost...

A smart meter is not a requirement to implement such an energy management system.

Integrated ZigBee low-cost controllers in a range of appliances from different manufacturers are a prerequisite.

• Proprietary communication protocols and energy automation software would make it very difficult and expensive to implement the desired level of control. 

If you are still connected to the grid, this level of control allows you to reduce the peak demand your household makes from the grid. This strategy helps:

• To reduce the need for network investment in extra poles and wires.
• To avoid the need for price increases for the electricity that you purchase from the electricity grid.

There are a number of businesses with Zigbee technology experience that could help manufacturers begin to offer versions of their appliances that are "ZigBee-enabled".

For example:

• Nanjing IOT Sensor Technology
• NETVOX ZigBee Smart House System