clean energy: grid infrastructure

Indiana is the second biggest coal-consuming state in the US. It is also among America's top 10 producers. So why has it just decided to ditch coal? The simple answer is cost. 

Having mined coal since 1830s, Indiana is ditching fossil fuel in favour of solar and wind because, says its major utility, the move will save consumers billions of dollars.

Indiana is not alone. In other US states, and in countries around the world, the cost of producing renewable electricity has fallen sharply, enabling solar and wind power to dethrone fossil fuels.¹

That’s encouraging news as cities and countries battle to cut planet-warming carbon emissions.

However, cheap and clean energy is of no use unless it’s delivered to where it’s needed, day and night without fail. This is where the power grid comes into play.

Power grids match the amount of electricity being generated with the load, or the amount being consumed. But today’s grid infrastructure, already under stress from extreme weather events such as hurricanes or wildfires, is ill-equipped to deal with the rush of renewables.

The intermittent nature of solar or wind means these power sources are also ill-suited for large-scale energy distribution.

This is why the world needs to develop advanced transmission infrastructure.

To investigate possible solutions, members of the Pictet-Clean Energy Advisory Board (AB) and the strategy's investment team recently visited the National Renewable Energy Laboratory (NREL) in Denver and the Electric Power Research Institute in Palo Alto, two organisations renowned for their pioneering renewables research.

There, our AB members saw for themselves advances in renewable energy technology, and were provided with fresh insights on infrastructure needs around the adoption of electric vehicles and the challenges and opportunities involved in integrating a growing fraction of renewables into the power grid.

Breaking the grid-lock

The current grid is based on a one-way system in which electricity flows from power plants to homes and businesses. It relies on alternating current (AC) for both long distance transmission and local distribution.

AC has changed little since its development in the late 19^th century, when it emerged victorious from the War of the Currents to become the standard for electricity grids worldwide.

Using a transformer, AC can be easily converted to different voltages. But its major shortcoming is that it loses power in transit. For a given voltage, an AC system has roughly twice the loss of a DC system, which can transmit energy more cheaply and efficiently over very long distances.

AC’s constraints become more obvious when it comes to distributing renewable energy because solar, wind and hydroelectric power is usually generated far away from where the energy is used.

Because of this, AC grids’ renewable capacity is limited to just 15 per cent of their total power mix, our AB members estimate.

Raising the percentage could destabilise the grid and lead to regular blackouts.

This is where DC could make a difference. 

power play

How UHVDC will accelerate integration of renewable energy in grid

In its modern form, ultra high-voltage direct current (UHVDC), is even more powerful, capable of using voltages as high as 1,100kV, compared with conventional DC’s 1.5kV.

UHVDC can also link unconnected AC transmission systems across different areas (see chart). This means a UHVDC-based macro grid lets operators tap into different clean energy sources hundreds or thousands of miles away throughout the day, and to effectively switch between sources depending on demand and weather.

Almost a decade after becoming the first country to adopt UHVDC, China debuted the world’s longest and most-powerful UHVDC line in early 2019. The new link stretches over 2,000 miles – more than the distance between London and Moscow. It delivers 66 billion kilowatt/hour of electricity from the country’s far northwest – home to abundant solar and wind power – to the heavily populated east, meeting demand of 50 million households.