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Photovoltaic self-consumption

22 May 2018

Voices such as self-consumption, distributed generation, net balance and others are currently being raised as the axes of a debate on energy policy, citizen participation and democracy.

The grid parity of photovoltaic energy has been a fact for a few years in Spain. 

This is one of the main factors that place the photovoltaic as a leader among the different sources of renewable energy, considering the energy transition, not as a future, but as a fact of global magnitude that is already here. In this sense, self-consumption has become an index of citizen participation in the inexorable transition from fossil fuels to green energies. Hundreds, when not thousands of articles endorse the benefits that the environment and the carbon pollution entails this unstoppable renovation. Each country faces this global challenge from its previous indices and parameters, but the response is general and at the planetary level. And each country should adapt itself to a normative level (the European Community recently issued a directive for the promotion of renewables with different indications regarding self-consumption as well as the level of innovation of its companies that intervene in the sector, accepting some challenges and challenges that the new times impose and that democratic citizenship demands.

The photovoltaic self-consumption phrase is on the street. But, what is self-consumption? As defined by the legal standard: "For the purposes of this law, self-consumption shall be understood the consumption of electrical energy coming from generation facilities connected inside a consumer's network or through a direct line of electrical energy associated with a consumer ". But on the street everyone understands that self-consumption is when the citizen installs his own source of energy. We speak of photovoltaic self-consumption when this technology is chosen for this purpose, technology that is highly hegemonic compared to other renewable sources in these devices. Where we say citizen we say legal subject, since it can be a person or collective (such as a collective of owners, or a building or facility of public ownership). What are the types or modalities of photovoltaic self-consumption devices?

In the first place, the device will be connected or not to the general distribution network.

The switched version requires a switch (sometimes integrated in the inverter) and an accumulation battery (which makes it more expensive), instruments that apparently "isolate" the device from the network, giving it the status of isolated from the network. Isolated systems, given their level of autonomy, do not have to confront the issues that networked devices face, devices that constitute the majority. One of the technical factors to be considered here is the degree of power of the device, which is generally less than 10 KW, apparently a frontier for the different aspects of the legal norm.

DSIPOSITIVOS CONECTADOS A RED.

The basic and problematic issue regarding the so-called self-consumption lies in this modality. The device connected to the network, will produce or not the energy it needs for its own needs.

If you do not reach the level of your needs you must take what is missing from the general distribution network. If the energy produced exceeds its own needs, it will have to pour the surplus into the network. Here a series of technical nuances are included, such as production time and consumption time, peak consumption, storage possibilities, facilities shared by different tenants, etc.

But the level of debate is established regarding the modality of consideration for this accounting of inputs and outputs between the Network and the Self-consumer. Obviously, each country tries to legislate these relations. And the basic models that are detected are

A highly clarifying and didactic article regarding this subject and referred to Spain is the one written by Amparo Balbastre, Delegate of UNEF in the Valencian Community, under the title "Analysis of RD 900/2015 of Self-consumption".

From this work we extract the following chart:

The controversial Royal Decree can be found at link

DISTRIBUTED GENERATION.

In previous paragraphs we had mentioned the Distributed Generation as a notion attached to self-consumption. We go on to expose some works that are dedicated to examine it.

According to the report Basic Guide of the Distributed Generation, edited by Fenercom.com (Foundation of the Energy of the Community of Madrid) in 2007: "There is no consensus on a global or European level, on what exactly is the Distributed Generation (DG), since there are multiple factors that affect its definition: employed technologies, power limit, connection to the grid, etc. "

According to this report, "The DPCA (Distribution Power Coalition of America) defines it as, any small-scale generation technology that provides electricity in points closer to the consumer to the transport or distribution network. On the other hand, the International Energy Agency (IEA) considers as GD only, the one that connects to the low voltage distribution network and associates it with technologies such as motors, mini and microturbines, fuel cells and photovoltaic solar energy ".

We see that the definition reflects the characteristic of the CLOSE TO THE POINT OF CONSUMPTION (for what is also known as generation in situ), in certain opposition to the concept of Centralized Generation, although it does not define the type of technology (source) in particular ( photovoltaic, wind, cogeneration, microturbines).

The aforementioned report also echoes the various criteria regarding the power ranges as well as the limit of this in the DG.

"The Department of Energy (DOE) of the United States, establishes limits ranging from 1 KW to tens of MW. In Spain, the Special Regime contemplates a maximum power limit of 50 MW. EscoVale Consultancy, prestigious consultancy in the United Kingdom, extends the range of powers up to 100 MW, limiting to 10 MW the maximum power for installations based on renewable energy sources ".

A notorious document regarding the subject that concerns us is that issued by the Orkestra Notebooks 2014/9 of the Basque Institute of Competitiveness, under the heading of Distributed Generation and Self-Consumption. Regulatory analysis, signed by Álvarez Pelegry, Eloy and Castro Legarza, Unai, and from which we extracted some other definitions of Distributed Generation:

- "For the Electric Power Research Institute (EPRI) are distributed energy resources from the management of small generating units from a few kW to 50 MW and / or energy storage devices, generally located close to the consumption of the distribution network or transformation centers ".

Again we see that it will be the decentralization and the proximity to the point of consumption, the main characteristics.

- "For the Institute of Electrical and Electronics Engineers (IEEE), distributed generation is that generation produced by installations of smaller size than the centralized ones, usually less than 10 MW, in order to allow the interconnection, at almost any point, of the system "

- "In Spain, distributed generation can be 'assimilated' to what Law 24/2013 of the Electricity Sector calls production facilities with specific remuneration but which, until its entry into force, became known as the special regime (Directorate General of Industry, Energy and Mines of the Community of Madrid 2007) ".

The Thesis of Master (2006) of David Trebolle, by the University of Comillas and entitled "The Distributed Generation in Spain" includes other definitions.

We outline the main characteristics that the DG has in the opinion of this author and that it includes in the conclusions chapter (p.151):

- Be connected to the distribution network.

- It is common for part of this generation to be consumed by the same installation and the rest to be exported to a distribution network (cogeneration).

- There is no centralized planning of this generation and it is not usually dispatched centrally.

- The power of the groups is usually less than 50 MW.

The magazine ROP (Revista Obras Públicas) of Engineers Channels and Ports, of Feb 2017, presents a monograph, by Antonio Serrano Rodríguez, under the title of Distributed Energy, where an article by the coordinator himself is published, entitled "Potentials of distributed energy in Spain . Fiction or reality ", in which our author asks: What do we understand by distributed energy? and answer:

"By distributed energy we understand the integrated process of production, storage, management and control of supply, demand, and community or local energy distribution, both in own networks of heating, electric power or other types of energy, such as the contribution to integrated networks already existing of productions and consumption under a common system, with differentiated management of the corresponding systems.

It includes, therefore, forms of energy distribution in traditional "procomunes", such as centralized heating, or production cooperatives / energy self-consumption, in general.

It also progressively integrates the possibilities of storage and management systems associated with smart grids that allow the inclusion of distributed electric vehicles, among others, electric vehicles, air conditioning systems, some domestic appliances, or the thermal storage capacity of buildings".

As we see it is a broad and extensive definition that ASSOCIATES another concept very close to Distributed Generation, such as SMART GRID. This English word is translated into Castilian as Intelligent Electrical Network (REI). It does not reflect as much as GD does the aspects of citizen claim, but it has more connotations of technological centralization.

It consists of the optimization in the management of electricity using computer technology to balance supply and demand, production and distribution. In practice, it is the computerization of the Electrical Network comprising all the data coming from the generation plants as well as the distribution routes and the final users.

Some of the objectives that are pursued (consistent with those pursued by the Distributed Generation) are: drastically reduce transport losses, facilitate connection to the grid and the integration of all types of renewable energy with percentage increases in energy such as wind or the solar, sustain the storage, distribution, etc. 

Off-The-Grid refers to isolated systems, totally autonomous, or off-grid. In a classification above we referred to these Isolated Devices of the Network. Grid Parity is the network parity, to which we also alluded at the beginning of this article.

Lastly, we summarize the main ADVANTAGES AND DISADVANTAGES presented by self-consumption in general and more specifically photovoltaic:

Advantage:

- High price of electricity rates.

- Lower dependence on the system.

- Decreases energy imports.

- Spain presents one of the highest irradiation rates in Europe.

- Use of an inexhaustible, clean and sustainable energy.

- Return to the effects of climate change.

- Reduces payments for CO2 emissions.

- Reduces the transport losses through the Network, which implies increasing the efficiency of the system.

- Reduced supply problems during peak hours.

- Generation of jobs by increasing the market for solar panels.

- According to Mariano Sidrach, Professor of Physics at the University of Málaga, (30/10/2017, 20minutos.es): "Self-consumption facilities have advantages only for citizens, for the electrical system, for our economy and for the environment "

Disadvantages:

- High purchase price of the systems. These have become ostensibly cheaper in recent years.

- Architectural difficulties.

- Intermittance of the generation for solar panels according to day / night cycle, which will require additional storage systems.

- Increases in network costs.

- Developments in specific regulatory regulations.

 

 

 

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