# Combined Heat and Power

Combined heat and power plants (abbreviated CHP plants) are power plants delivering energy in the form of a combination of heat and electric. In Trident, energy produced in either form goes directly into the power balance for the local area, with different marginal cost for the two types.

The power plant will provide the two types of energy in varying ratio depending on the temperature in the local area. Nominally the amount of heat energy delivered is highest during cold weather, but this is user configurable by a heat-ratio xy-curve.

## Setting up a CHP plant

Please refer to the [Logical model view API](lmlmv) to see what fields must be supplied when creating a chp plant. The plant must be associated with an area and have an unique id. It's also required to supply a reference to both the temperature time series and the temperature-ratio function. These can be shared between chp plants.

Please refer to the [Python API](modulechp) to see what input data is needed for each plant. Each plant must have:
- An associated total capacity series 
- A function between temperature and the ratio of heat energy production
- Cost of electric energy production and heat energy production
- A temperature series associated with the plant. **Note:** These can be shared between objects.

Output result series is found in the [Python API](modulechp). Please note that there is not a single output for electric energy produced, only the total and the part that is heat.