The flexibility is the capacity of the consumption unit (CU), like a customer installation to adjust and curtail resources (like electricity consumption), according to grid needs, as to compensate peak moments, and to customer production processes and comfort.

The main goal of Grid Operators (like Red Eléctrica in Spain) is to keep the balance between generation and consumption in the electric system. When an unexpected peak happens, the System Operator asks for a production increase (up) or a decrease (down) to compensate it.
On the other side, it can ask to intensive energy consumers for a spot curtailment from their energy flexibility to balance it.

Unexpected peak moments can be compensated in different ways: through the interruption service in installation, governed directly by Grid Operators, which turn energy supply off during the needed timeframe.
Or with load shifting, when the production process loads are anticipated or postponed to different time. For instance, in a heat pump, it is possible to shift before or afterwards the heating of the liquid for the thermal transmission, as long as to be able to respect the working constraints of the device, like the temperature.
Finally, to adjust the working parameters of devices comes with a fine tuning for safe, efficient and tailor-made regulation of unnecessary and unproductive consumption. So, this implies a reduction or an increase of resources, governed by intelligence, for the Consumption Units (such as factories, building or electric vehicle charging stations).

The Distributed Energy Resources (DERs) are an aggregation of flexible distributed resources able to participate in the demand flexibility. They come from production plants (small or industrial), battery storage (domestic or industrial), finally those bi-directional for the vehicle to grid.

A Consumption Unit is a facility where energy consumption is needed for a production (i.e. a steel plant or a paper machine) or comfort (i.e. HVAC) process. For instance, building or uni-directional electric vehicle charging stations.

It is an installation to generate electricity from renewable sources or fossil fuels (i.e. coal or natural gas) to be injected in the electric grid.
The size can be small, as residential, around 15 kW or industrial from 100 kW.

The batteries (domestic or industrial) can participate in the market with their fast discharge and capacity, when aggregated into a flexible distributed storage system.

An aggregation of flexible distributed resources allows to deliver a governance of consumption from different installations. A VPP (Virtual Power Plant) is a virtual aggregation to generate energy flexibility, to enable grid operators to dynamically compensate unexpected peak moments along the days.
The virtual aggregation nourished with demand flexibility turns into a key source to mitigate peaks and congestion in micro grids.
Through an intelligent governance which connects all these distributed resources, it is possible to create a DER, so a system to participate in the balance services market without polluting and increasing the unbalance costs for the Country electric system.

To build a demand capacity network means to aggregate flexible distributed resources, alongside the Virtual Power Plant, which dynamically generates asset to be traded in the balance market through an aggregator.

The demand aggregator is a broker who trades the demand flexibility in the electric market, such as balance service one.
This subject sells these assets to generate new revenue streams for the end-users and to turn the electric grid more secure, resilient and flexible, and compensates the unprogrammable availability of intermittent resources..

To participate in the flexibility system is an advantage for the grid operator, as well for end users: the energy market will reward the capacity and the flexibility.
Capacity fees: they are the reward for end users for reducing the consumption when the markets need, according to the flexibility calls. They are available in some EU Countries where it is established a fix price (€/MW) for the available power.
Flexibility fees: they reward the actual flexibility (€/MWh) available during the calls. They are available in some EU markets.

This is the fine for the subjects who breach the committed flexibility for their contribution in the unbalance of the grid.
Capacity fees: they are the reward for end users for reducing the consumption when the markets need, according to the flexibility calls. They are available in some EU Countries where it is established a fix price (€/MW) for the available power.
Flexibility fees: they reward the actual flexibility (€/MWh) available during the calls. They are available in some EU markets.

The baseline is electric consumption that an end user would have consumed in absence of an energy efficiency or flexibility control mechanism: it is actually the difference between the expected consumption and the real one of the installation.
That flexibility activation is to be manage to guarantee the commitment with the grid operator, without generating a divert from expected operations, which will be fined with the unbalance prices.

To activate a consumption (energy efficiency) and flexibility control system means to deliver a way to control green house gasses (GHG) emissions. So, by enhancing an installation with an intelligent governance, you can then control CO2 emissions too.
From an actual consumption measurement, it is possible to calculate the carbon footprint of an installation, through standard conversion tables between electric supply and GHG emissions.

The PPAs are bilateral (between two parties) agreements for the future supply of electricity from renewable resources, like wind or photovoltaic farms. The electricity comes from a specific plant or from flexible distributed renewable resources and compensates the needs of an end user along the agreement duration. The main agreement types are: physical supply or financial (swap) to fix the price for the future supplied energy. They are mid long term ones.
These agreements are medium or long term.
The price is the peculiarity of the agreement. The energy transactions define the amount of supplied asset from source to destination to be paid, while the economic transaction is the value of the contract according to the consumption, at the agreed price.

They are the objectives, standardised by United Nations, which define where businesses and government are willing to focus to develop net-zero emissions for their ecosystem.