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Direct Current Meets New Demands

Paul Kando

A new study published in Nature Energy by scientists at the International Institute for Applied Systems Analysis (IIASA) shows that changing the way we move around, heat and cool our homes, and buy or use devices and appliances can help raise living standards while also staying within 1.5°C above pre-industrial levels — the target set by the 2015 Paris Agreement. Improving living standards need not increase energy demand.

The study is the first to show how the 1.5°C target can be met without relying on unproven carbon capture measures. Social, behavioral and technological innovation combined with policies that support energy efficient low-carbon approaches can reverse the steady growth of energy demand. Downsizing the global energy system makes it more feasible to transition from fossil fuels to renewably generated electricity, providing for development needs while limiting the impacts of climate change, the study concluded.

The research examined a number of innovations currently at the fringes of the market. Once mainstreamed, these could help reduce energy use and emissions two to fourfold—in transportation, homes, offices, and manufacturing. Shared and 'on-demand' fleets of energy-efficient electric vehicles with increased occupancy can cut 2050 global transportation energy demand by 60%, while also reducing the number of vehicles on the road. Using multifunction digital devices like smart phones to access services — instead of owning goods — can reduce the otherwise explosive growth in global energy demand by as much as 85%. Strict energy performance standards for buildings, new and renovated, can reduce heating and cooling energy demand by 75-90%. Shifting to a healthier diet with less red meat can significantly reduce emissions from agriculture, while also increasing forest cover to absorb CO2.

If global energy demand is reduced by 40%, current rates of renewable energy deployment could more than meet the world's energy needs. The report shows how reversing global emission trends can support rising living standards, cleaner air and improved health worldwide. 5-12% of the electricity generated in the US is dissipated as heat while traveling through transmission and distribution lines — a loss that increases with distance — and through transformers, which consume power as long as they are connected. Using local energy sources and direct current (DC) microgrids could eliminate these losses.

A lot of high-power electrical equipment and machinery used in industry, buildings and transportation worldwide runs on DC power. In homes and offices the use of DC powered digital devices is commonplace. Most modern appliances incorporate electronic controls that require DC current to operate. When these devices are operated on standard AC current, they rely on their own “power packs” — devices that convert AC to DC power, which consume electricity.

Solar panels generate, store and deliver DC power, which other means of power generation could also easily provide. Solid state, 95% or more efficient, DC to DC power converters can match voltages to user needs, eliminating the need for AC power-robbing transformers. But introducing DC system-wide is a challenge, especially here in the US. The lack of certified DC power equipment, household and consumer devices, and trained, experienced professionals is problematic. It is difficult to find an architect, electrician and builder, or refer to a code that specifies DC system details.

But there are 3 billion people worldwide with no reliable access to electricity and 1 billion still cook over dung or fossil fueled fires — a potential market certainly not lost on China and the European Union, both of which have AC-dominated power grids similar to our own. DC will eventually come to rival AC in power grids and electrical systems. Energy efficiency is higher, and there are advantages when moving power long distances. DC also has significant potential to advance sustainable energy agendas. Engineering groups are already at work on a worldwide low-voltage DC standard, as well as DC standards for lighting, appliances and meters.

All-DC electrical systems augmenting the Passive House (PH) building standard could ultimately decarbonize the building sector. PH already reduces heating and cooling needs by up to 90% compared to conventional construction. Incorporating rooftop solar panels and all-DC infrastructure and appliances into PH design could even contribute clean energy to neighborhoods and communities through DC microgrid networks, aggregating surplus power and resources, such as energy storage capacity, and providing grid services on local and larger scales.

The global community from world leaders and multinational corporations down to individual consumers and citizens needs to act in concert to avoid dangerous climate change while improving human wellbeing, declares the IIASA report. Local efforts could become models for regional and even national action to eradicate energy poverty, establish energy democracy and greatly enhance grid security and resiliency. Our common future depends on our active participation.