Creating a storage enabled smart grid

September 10th, 2015, Published in Articles: Energize

 

With the rise of coupled solar and storage systems, there are challenges which must be addressed, notably claims of grid instability resulting from solar generation. A careful examination of the current situation from different perspectives, and proposition of viable solutions is necessary.

There are two main challenges today in the solar photovoltaic (PV) market: the first being the massive supply of solar power, specifically the midday solar production peak to the grid, and the second is managing the evening consumption peaks from the grid where the load is at its highest. The natural monopoly of the grid and the complete power transmission infrastructure is a reality that the renewable energy industry must work with. As renewable energy and storage continue to rise, it is important to take a second look at the current grid situation from a different angle.

To the grid, are solar and storage systems friend or foe?

It is no surprise that many states have been striving to cope with the initial solar feed-in boom, where the totality of solar production is fed to the grid. Grid companies report that this practice has clearly exerted immense pressure on their ageing grid infrastructures and power lines. A logical equation is; the higher the consumption, the higher the need to reinforce the electric lines. This argument against the solar industry cannot be ignored, and needs a serious take on the topic. Can one work in isolation of the other, or can both industries integrate the technologies to create a homogeneous democratised energy platform?

Adaptability of the grid to the new electric usages

The number of indispensable electric appliances such as  computers, air-conditioners, heaters, electric cars, etc., has increased in the recent years compared to previous generations. In our modern societies, as well as in fast developing countries, rising living standards and urbanisation are reaching unprecedented rates. The International Energy Agency (IEA) projects a rise in European electricity consumption at an average annual rate of 1,4% to 2030, with a doubling of renewables in Europe’s electricity generation from 13% to 26% in 2030.

In the developing world, specifically African markets, urban growth during the last two decades is reaching rates of 3,5% per year which is expected to continue into 2050, according to the African Development Bank. Facing the current rise in electricity consumption in developed and developing nations alike, the grid is indeed experiencing strenuous demand pressures with concerns of unbalanced supply. We know that constant electricity supply is a prerequisite for economic development and advancement. Urbanisation is impossible without electricity.

 

Fig. 1: Daily consumption and impact on the grid voltage (Source: IMEX CGI  smart grid energy consultancy, France).

Fig. 1: Daily consumption and impact on the grid voltage (Source: IMEX CGI
smart grid energy consultancy, France).

The grid does not seem to be adapted to handle the growing needs of our post-modern society. Taking the example of the rise in number of electric cars, which consume large amounts of electricity to charge, further hikes in consumption will further increase the pressure on the grid. The entire grid network must be revisited, and the number of power plants must be increased. These expensive interventions will need to be implemented to keep up with the same fast rate as the development of technologies and industries. What must be examined, is whether there could be a way to develop the grid without incurring the high cost of building new power stations.

Mixing evolving technologies proved to succeed

If we consider the telecommunications industry, which previously used copper wires and has developed vastly to incorporate an elaborate mix of possible solutions: maintaining the operation of the old lines, adding satellite communications, mobile telephony, and upgrading to optical fiber. This mix has been successful by accepting the evolving global consumption trends in the telecom industry.  Just as the telecom industry has upgraded and continue to evolve, so too must the electricity network, taking into account renewable energy and storage solutions.

Let’s take an example of a farmer who invested in renovating his professional space to upgrade his machinery, consequently also increasing his electricity consumption. He would need a three-phase 230/400 V AC connection to be safe. The challenge is that he is located in an area at the end of the electricity line, where as a consequence he is therefore subjected to frequent low voltages and the non-operation of some of his appliances. This is a micro example of grid congestions, voltage fluctuations, circuit overloads, burned electricity lines among other concerns that eventually cause black outs or brownouts.

Pertinent questions regarding the deployment, cost of maintenance, recreation, or expansion of a national grid level as well as building new electricity stations, are related to these unanticipated voltage fluctuations at the end of the electricity lines outside of the urbanised clusters. That being said, electrification of isolated sites both in the developed and developing world, is yet another challenge, in addition to the economic and geopolitical situation of certain countries where infrastructures are destroyed or dysfunctional. A grid-interactive durable alternative is the only way out. It is clear that the need to better understand and manage the integration of new power generation and storage technologies into the grid is more pressing than ever.

Embarking on the new Solar 2.0 revolution

The foundation of a smart grid as defined by the European Commission in 2009, is an electricity network that can integrate in a cost-efficient manner the behaviour and actions of all users connected – generators, consumers and those that do both – in order to ensure an economically efficient, sustainable power system with low losses and high levels of quality and security of supply and safety. The systems of generation; conventional and renewable energy, regroup the ensemble of the energy sector’s production capacity. A local system plays an important role in the activation of energy intelligence in the residential, commercial and industrial sectors in terms of the integration of renewable energy, smart inverters, storage systems and electric vehicles.

Solutions for optimal integration of renewable energy into existing infrastructures

The integration of renewable energy represents the main challenge for distribution system operators. In fact, these resources present some constraints: intermittency, fluctuation, and often a potential gap between consumption profiles and production. These constraints can be either reduced or elevated according to the geographical area and the demographic profile of consumption. For example, from a residential perspective, the load profile is not always in direct relation to the solar production profile (Fig. 2).

Fig. 2: Production and consumption variation (Source: IMEX CGI smart grid energy consultancy, France).

Fig. 2: Production and consumption variation (Source: IMEX CGI smart grid energy consultancy, France).

However, re-examining the situation from a larger perspective, that of a district or city, it appears mostly that the profile of consumption would fit as a perfect match with the solar production. We speak about what is called in French “Foisonnement”, the closest definition as balancing aggregation. Proliferation defines the adequacy production vs. consumption and allows the balance and stability of the infrastructures.

We can define this phenomenon in this way, as the difference between the amount of the entire instant production and instant consumption on a defined mesh of an electricity network. If the result is close to zero, the “foisonnement” is optimal, as the immediate production is instantly consumed.

Tangible solutions already exist to improve this balancing aggregation

Comparing different types of end-users with complementary load profiles on a defined zone: residential with morning and evening electricity consumption, industrial and tertiary with higher demand of consumption during the day. By combining these different profiles, it is possible to obtain a regular, and stable, consumption load profile (Fig. 3).

Fig. 3: Example of “foisonnement” or balanced aggregation in the French Brittany region.

Fig. 3: Example of “foisonnement” or balanced aggregation in the French Brittany region.

A combination of different types of power producers: wind, solar, thermal, hydraulic or nuclear, each source complementing the production profile of the other. The goal is to maintain a balance in the energy mix and to obtain a production profile close to the consumption profile, which would therefore be the ideal aggregation.

On the other hand, in rural areas, there is a much greater gap between the supply and the demand. For example, a solar park in a scarcely populated area or a factory consuming large amount of power in a remote site without enough supply. This situation results in high network imbalance, with common voltage collapses, frequencies variations and recurrent grid failures.

Control and load management

In zones where physical solutions cannot be applied, other technological alternatives such as load shifting and control can be useful to perform targeted actions of grid support and load management:

  • The control of defined loads/consumers: When the available energy in a certain zone is higher than demand, the distribution network operators activates the loads. This is an example of the automatic activation of appliances during off-peak hours the can be adapted to the profile of renewable energy production. When the consumption on this zone exceeds the amount of produced energy, the distribution network operator deactivates the loads. This load shifting technique improves the integration of renewable energy to the existing infrastructures by limiting the disruptive consumption and production peaks.
  • Smart control of storage systems: Charging batteries when the renewables’ power supply is higher than demand, and discharging them when the production is lower than the consumption represent a viable solution to balancing the grid supply and demand.

Mass storage and self-consumption solutions

Storage solutions present an undeniable advantage as they can be used at different scales: cities, districts, individual or clusters of homes. With storage, there would be no need to perform modifications on the existing grid, rather the grouping of “small” solar systems coupled with residential storage solutions. This efficient management of grid energy flows, optimises the aggregation balancing, and integrates clean carbon-free energy production without disturbing the current infrastructure.

Technological progress in recent years has resulted in storage efficiency improvements (lithium, redox), which when combined with new generations of smart grid inverters, will introduce more efficient solutions and energy source management. Such smart grid inverters handle multiple energy sources: photovoltaic, battery, and grid, provide real-time analysis of production and consumption, and will progressively start replacing conventional grid-tie or off-grid technologies. What further revolutionises this trend is the possibility to avoid feeding-in solar production to the grid, but rather to consume at night, when consumption needs are the highest, what they produced during the day and store the surplus in batteries, and injecting into the grid only what is left over after the batteries have been charged.

These state of the art inverters, based on the high efficiency architecture of grid-tie inverters, are the only solution to be actively connected to the grid while managing direct self-consumption and battery management at the same time. Such systems must therefore be interconnected and communicative (M2M) to create intelligent clusters allowing to supply network services to the distribution network operators of electricity infrastructures.

A vision for a smarter tomorrow

The world of energy is indeed transitioning. Revolutionary renewable energy developments are obliging ancient energy players to revisit their entire business model. All energy participants are preparing for grassroot change, as it obvious that one player must work in parallel with the other, and not in opposition.
Carbon-free energy and storage will not be a constraint anymore for developing networks, but rather storage systems will now be the driving force behind new electrical infrastructures.

This transition must be performed in constructive steps:

  • Harmonisation of regulatory framework, re-adaptation and implementation of new economic models: steps such as the changing of energy purchase prices can be promising. The principle of selling instantly produced energy may remain, but more favourable conditions may be proposed, such as purchasing generated or stored power “on demand”, which would enable servicing the grid network.
  • Creation of a new domain and expertise focused on network management and aggregation: either externally or integrated within the operator’s structure can expand employment creation. The new duty would consist of handling applications such as storage capacity, controllable loads distributed within the electrical infrastructure for real-time management of energy flows, and support and automated load management.
  • Common communication and exchange between concerned parties are necessary: network administrators, aggregators and manufacturers of storage solutions and smart inverters, in order to relate and integrate their latest innovations to the network. Smart-grid inverters and storage management represent real technological breakthroughs and will constitute a fundamental component of the smart grid networks of tomorrow.

Besides the technological and regulatory aspects in a world where energy and growth are interlinked, the perspectives of new developments of smart grids give a vision of an extraordinary social and economic benefits of tomorrow’s electrical infrastructure.

Contact Taiseer Khalil, Imeon Energy, contact@imeon-energy.com

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