HOMER Energy Support

Modeling zero energy buildings

Last Updated: Jul 25, 2016 03:06PM MDT

Can I simulate different grids, different regulation strategies for building (system)-grid interaction i.e. :

1.       Regulation strategy: the building cannot sell the energy  at any time it wants, but this is regulated by the utility when it is possible

2.       Regulation strategy: utility requires from the building that the fed back energy should be the same  quality as the purchased energy.

You have written that the system (building) may purchase power from the grid part of the time, and sell excess power to the grid part of the time and how HOMER controls , when the system is purchasing and when selling? Can I as a user have any influence on this, make some regulations for this interaction, what are the assumptions behind purchasing and selling energy for the system (building) point of view.


On the Advanced tab of the Grid Inputs window you can prohibit grid sales when the sellback rate is below some value.  That gives you good control over when the system can sell power to the grid because you can set up the grid rate structure any way you want.  You could, for example, prohibit grid sales whenever the sellback rate is below $0.01/kWh, and then set the sellback rate to zero in any time period you want to prohibit grid sales.

HOMER doesn’t currently give you much control over when the system can buy power from the grid though.  You can use a few tricks though, depending on the type of system you are modeling.  For example, if the system contains a generator, you can schedule it to operate during times that you want to prohibit grid sales.

In HOMER, we call the amount of energy purchased from the grid minus the amount of energy sold to the grid the ‘net grid purchases’.  On the Advanced tab of the Grid Inputs window, you can set a maximum allowable value for the net grid purchases to any value you want, including zero.  If you set the maximum net grid purchases to zero, you are requiring the system to sell back at least as much energy as it purchases from the grid.


Is HOMER the right software to simulate one grid-connected building? 


HOMER does not model the thermal performance of the building (insulation, solar heat gain, etc.) but it will do a good job of modeling the building’s electrical production and consumption.

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