Smart grid power connections for renewable energy development

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Dr Lou Sai LEONG

Further to my previous article (Facts and Issues of Energy Production, published in April), I would reiterate that the most important issue for the development of renewable energy production is the energy storage. Unless there is provision for storing a huge amount of energy produced, the level of renewable energy production must now be confined to either the level of consumption or from the other energy resources. Until now, countries around the world do not rely on just one type of energy, like renewable energy, but opting for multi-resourced energy in their strategic development of their resources.

Moreover, the most efficient management of energy production is the smart grid energy production network (SGEPN).


The SGEPN has been in place for decades while technologies have been improved over time. SGEPN links together energy production within a large area in a network through the Ultra High Voltage Transmission Current. In this network, energy from power plants is redistributed to the areas where the energies are in great demand.

In light of this, some experts have proposed to use SGEPN mainly for renewable energy.

For example, on a cloudy day with no wind, the area can get electricity imported from other regions which have solar or hydraulic energies or windy area with energy production to meet the demand during the peak consumption period. In China, energy can be transmitted from the west region to the east coast. Or, from North Russia to Southern India.

In this connection, let us discuss about electrical transmission.


Electrical transmission is a bulk movement of electricity from one generator to a substation by interconnection lines. There are generally two types of currents for transmission: high voltage alternative current (HVAC) and high voltage direct current (HVDC). Despite HVAC type current having industrial applications, HVDC is more appropriate for electricity transmission over long distances.

Figure 1: Comparison AC and DC

Figure 1 shows the relationship between the construction cost and the electricity transmission distance for both current types. If the distance is shorter than the even-break point (< 800 km), AC is suitable. However, if the cable is longer than 800km, DC is more cost-effective for the long distance transmission.


Nevertheless, there are constraints to constructing long distance cable due to construction cost and energy loss. The price of transmission line construction is linearly increased as shown in Figure 1. The energy loss is due to the resistance of electricity transmission. To reduce energy loss, we need to either reduce the thickness of cable (but that would reduce the power) or increase the high voltage. The high voltage is limited nowadays by current technology and geological constraints. In USA, the highest voltage of electric power transmission built there has been “ultra-high-voltage DC” as referred to 800 kV. Yet, China has significantly improve the technology by building the highest voltage power transmission cable in the world, for both AC and DC, up to 1000 kV.

Given the high cost, various constraints and technical complications, the transmission of electricity from a power plant to the substation for electricity redistribution through DC lines can attain up to 2000 km in the most economical and cost effective development (based on existing construction capability of China).


Would it be possible to replace completely the current energy production with renewable energy production through SGEPN for all our electricity needs?

Figure 2: Idea project of transmission cable network in China and in Europe

Figure 2 shows the concept of building a smart grid network of high voltage from different renewable power stations located in a large area of one or several countries. This is extremely challenging in terms of the scale of power network, especially when we need to address two major issues.

A) The first issue is more related to cost of construction than the technology itself. As mentioned, the building cost is extremely high and it is not affordable, given the high maintenance cost of the stations. The actual electricity bill will cost much more. Realistically speaking, each country (each province) must consider its own capabilities and geopolitics when considering international projects.

B) The second issue concerns the scale of the SGEPN. In a large country like China, 2000 km regional scale power grid network is insufficient to address the correlation of variation of its weather. For example, if a typhoon hits an area, which covers hundreds or more than a thousand kilometers, the wind speed is so high that it is not possible to turn on the wind turbines to generate neither wind nor solar power. As a result, the fossil-oil power station becomes the last resort because it gives faster response in generating electricity. In addition, most of the renewable power stations are built far from the cities, especially in a country like China with special geopolitics. Although most of its major cities are in the east coast, renewable power stations which are more conveniently built in the west with lower population can transmit energy supply to the eastern cities.


In the short and medium terms, we cannot rely solely on renewable energy. The existing supply of energy through SGEPN is already sufficient to supply our current consumption need.

My view is that, our most urgent mission now is to tackle climate change by reducing CO2 emission. To achieve this goal, we must reduce the fossil-oil based energy and increase the non-CO2-emission energy. We must start by developing several types of energies (Nuclear, renewable energy, biomass, thermal heat, etc.), combining the SGEPN with suitable transmission electricity connections to manage the production more efficiently. When the technology of generating high voltage is improved, reducing the cost of transmission lines construction, resulting in skilful management of SGEPN (improved efficiency of each production source power, countries’ broader security guarantee, regulation of AC/DC by different companies, climate change, etc.…), it then becomes possible to replace non-renewable energy power plants with renewable energy.

About the Author

Dr Lou Sai Leong is an expert analyst providing nuclear measurement solutions in the fields of nuclear decommissioning and nuclear waste characterization. She manages and executes several projects as well as being promoter of nuclear measurement services in Japan.

She obtained bachelor degree in fundamental physics in 2008 in Université de Paris-Sud, then obtained the master degree in Nuclear engineering in 2010 in Université de Pierre et Marie Curie. Later, she was specialized in nuclear physics and nuclear data measurement, and obtained the PhD in Université de Paris-Sud in 2013.