The self-consumption of electricity from a photovoltaic system is one of the best solutions to reduce the costs of energy bill. For energy-intensive companies the investment becomes very profitable.

The energy bill is usually divided into three components:

• a variable amount expressed in c€/kWh proportional to energy consumptions

• a power quota expressed in c€/kW per year. The reference value is the contractually committed power or the maximum value of the power used in the month

• a fixed fee expressed in euro cents per withdrawal point per year – €/wdp per year.

The components proportional to energy consumption are the predominant ones in the composition of the energy bill, even if the components proportional to the engaged peak power are beginning to have a greater importance.

Self-consumption contribution has 2 main impacts on the power grid consumption curves:

– more or less significant reduction of the energy withdrawn from the electrical grid

– more or less significant reduction of power absorption peaks from the electrical grid. This effect, called “peak shaving”, is more significant if the power absorption is concentrated in the central phases of the day, when the photovoltaic plant delivers its maximum power.

In a self-production system, the maximum efficiency for the consumer is obtained by:

• acting on the term related to consumption, reducing the energy withdrawn from the grid

• limiting the maximum power withdrawn, reducing power peaks concentrated in the phases of maximum production.

Examples

We report some simulations for industrial users, divided by consumption conditions and installed power on the industrial coverage.

Case 1

Consumption 5/7, h 24/24 – Food & Beverage Company

500 kW PV system installed in Northern Italy

By increasing the power to 1,000 kW or for installations in South Italy, the percentage of savings due to self-consumption increases to values of 14-16%.

Case 2

Consumption 7/7, h 24/24 – Logistics of cold

500 kW PV system installed in Northern Italy

By increasing the power to 1,000 kW or for installations in South Italy, the percentage of savings due to self-consumption increases to values of 10-12%.

Case 3

Consumption 5/7, 12/24 h – Manufacturing Company

500 kW PV system installed in Northern Italy

By increasing the power to 1,000 kW or for installations in South Italy, the percentage of savings due to self-consumption increases to values of 15-20%.

Generally, by increasing the power of the PV system there are always advantages in terms of investment. The only limiting factor is the available space on the roof, because the power is proportional to the number of installed photovoltaic modules.

Energy sales mechanisms in Italy

The energy not consumed instantaneously, unless considering storage systems, is sold and remunerated through the regulations of the electricity market.

Dedicated Withdrawal (RID)

The RID is a simplified method for selling electricity produced by the PV plant. It consists on the sale of electricity to the Energy Service Management company (GSE) and replaces any other contractual fulfillment concerning access to dispatching and transport services. Any production systems powered by renewable sources are eligible for the RID regime.

On-site Exchange (SSP)

The SSP allows the economic compensation between the value associated with the electricity fed into the grid and the value associated with the electricity withdrawn and consumed in a different period. Power plants up to 500 kW powered by renewable sources can access this electricity mechanism (the power limit is 200 kW for power plants with commercial operation date before 31_st December 2014).

Direct sales on the electricity market

By qualifying as “Dispatching Users and Market Operators” it’s possible to sell the energy produced by renewable energy plants through trading and buying/selling operations. For small energy producers with a single or with few photovoltaic systems the operation isn’t convenient, but it’s possible to rely on companies specialized in the sale and trading of energy.

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