View source for DER VET User Guide/Technologies/Combined Heat and Power

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Combined heat and power (CHP) simultaneously generates electric power and thermal power in the form of hot water or steam. 

In DER-VET, steam can be converted to hot water with no penalty (thermal technologies that generate steam can generate the same kW of hot water while consuming the same amount of fuel). But, hot water cannot be converted to steam. 

The amount of electricity, steam, and hot water generated by CHP are constrained by two key ratios, the electric:heat ratio and the max steam ratio. These are covered in more detail in the inputs section below.

In some cases, the thermal generation requirements on a CHP may induce the CHP to generate more electricity than is allowed by a no-export constraint or some other power flow constraint in the rest of the system. To avoid infeasibility issues in the optimization, electric power may be dumped in situations like this. 

= Inputs =
== Rated Capacity ==
{| class='wikitable' style="width: 95%;"
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|style="width: 10%"|Tag
|style="width: 20%"|Key
|style="width: 70%"|Description
|-
|CHP
|rated_capacity
|The maximum electric power generating capacity of the CHP in kW of electricity. This does not include any thermal power generating capability of the CHP, but the two are related through the electric:heat ratio. Optimal sizing is not allowed for CHP.
|}

== Electric:Heat Ratio ==
{| class='wikitable' style="width: 95%;"
|-
|style="width: 10%"|Tag
|style="width: 20%"|Key
|style="width: 70%"|Description
|-
|CHP
|electric_heat_ratio
|The ratio of electric power generated by the CHP to thermal power (both hot water and steam) generated by the CHP. This ratio is constant and will not change depending on the thermal and electric generating requirements on the CHP. Instead, thermal or electric power may in some cases be dumped to meet optimization feasibility requirements.
|}

== Heat Rate ==
{| class='wikitable' style="width: 95%;"
|-
|style="width: 10%"|Tag
|style="width: 20%"|Key
|style="width: 70%"|Description
|-
|CHP
|heat_rate
|The efficiency with which electric power is generated in the CHP. This is the MMBTU of fuel required to produce 1 MWh of electricity, regardless of how much thermal energy is generated concurrently. 
|}

== Max Steam Ratio ==
{| class='wikitable' style="width: 95%;"
|-
|style="width: 10%"|Tag
|style="width: 20%"|Key
|style="width: 70%"|Description
|-
|CHP
|max_steam_ratio
|The maximum steam power to hot water power ratio allowed by the CHP technology. Since steam can be converted to hot water but hot water cannot be converted to steam, this parameter sets the maximum amount of steam that can be generated for a given amount of hot water generation. For example, a CHP system that generates 1 kW of power in the form of steam for each 1 kW of power in the form of hot water would have a maximum steam ratio of 1. This example could see the CHP generate entirely hot water, but will never generate entirely steam.  
|}

== Fuel Type ==
{| class='wikitable' style="width: 95%;"
|-
|style="width: 10%"|Tag
|style="width: 20%"|Key
|style="width: 70%"|Description
|-
|CHP
|fuel_type
|The type of input energy that powers the CHP. Either 'liquid', 'gas', or 'other'.  
|}