“I just need power, I don’t need heat.”

A power station, whether a petrol-, diesel- or gas power station, consists of two main components:

1.       the combustion engine

2.       the generator

ad 1:      All of these engines are combustion engines. In these engines you burn some kind of “fuel” together with outside air. The explosion or expansion of the air moves a piston which turns the engine crankshaft.
A large part of the energy you pump into this process results in heat. The rest of the “invested” energy drives the shaft.
In your car the shaft drives the wheels, in a plane it turns turbine or propeller; in a power station the shaft runs the generator.
The efficiency of a power generator is defined by the ratio between the energy you transfer into rotation energy compared to the total energy input.

ad 2:      the generator turns the rotating power into electricity/power we can use.

The heat comes out of the generator mainly in three forms:

• motor cooling water: 
  the constant burning process inside the engine cylinders heats up the engine itself. The motor cooling system transports the heat in form of hot water (about 90°C) out of the engine where the motor cooling water gets chilled back to about 80°C before it circulates back to the engine again (thermal energy of around 2,5kWh). In gas or diesel generators where you don’t use this thermal energy it has to be “destroyed with chillers which consume electrical energy.
• exhaust gas: 
  while the air enters the engine with outside air temperatures, the burning of the fuel heats it up to temperatures of 500°C and more (thermal energy of around 2,5kWh). If there is a thermal demand bigger than the heat from the motor cooling you can use an exhaust gas heat exchanger to use the main part of this energy as well. This normally gets done in areas with a larger heating demand. In this case the exhaust gas leaves the chimney with only about 120°C instead of about 500°C.
• radiation heat: 
  As the cooling water enters the “cold” side of the cooling system with about 80°C, the engine itself is still too hot to touch by hand. This heat gets cooled back from the ambient air (waste heat of about 1kWh).

There is no way to run any gas or diesel generator without heat generation.

High efficient gas generators achieve an electrical efficiency of more than 40%:

One m³ of natural gas contains about 10kWh of energy.

Burning 1 m³ natural gas in a gas generator results in about 4kWh of power.

The remaining about 60% or 6kWh leave the gas generator again in form of heat.

Whether or not you can take advantage of the thermal energy depends on your own facility, but has no influence on the amount of electricity coming out of your generator (see CHP).

“My generator generates 100% power, nothing else.”

This means that you only use the electrical power of your generator; you don’t take advantage of the heat you get for free. You need chillers to cool back your motor cooling water continuously which consumes electrical power (see CHP).

“I just need power, I don’t need heat.”

Whether or not you use the heat, has no influence on the electrical power you receive from your generator (see CHP).