With the New Year upon us, let's take a few moments to consider the major sustainable energy trends in business from the past year. Many of these 10 trends represent milestones achieved in 2013 as the result of years of dedicated efforts. Others are of a more short-term nature. Each, however, played a big role in 2013.

1. 100-percent renewables: Why go halfway?

At least some degree of reliance on renewable energy belongs in virtually every corporate sustainability strategy. But for a growing number of companies in 2013, nothing less than 100 percent would do.

The U.S. EPA's Green Power Partnership includes more than 700 organizations — from Fortune 500 corporations to mom-and-pop shops to the public sector — that rely exclusively on renewable energy to cover their electricity use in the U.S. through a combination of green power purchases and on-site renewable energy systems. The EPA's growing list of 100 percent green energy users includes only the U.S.-based operations of organizations partnering with the agency, but it shows a cross-section of those whose bold sustainability strategies are setting the trend.

Joining the EPA's 100 percent club for the first time in 2013 was chipmaker Intel Corp., which also ranks as the top renewable energy consumer in the program by using more than 3.1 billion kilowatt-hours (kWh) annually. Other notable names on the all-green starting team are Kohl's Department Stores, Staples and Whole Foods Market.

In addition to companies already at 100 percent, many businesses in 2013 added all-in renewable energy targets to existing sustainability strategies, or made serious progress toward meeting previously stated 100 percent green power targets.

Lisa Jackson, who as EPA administrator took responsibility for building closer relations between the agency and the private sector, now is helping Apple on its own road to 100 percent renewables, which she recently discussed at VERGE SF in her first appearance before a business audience, and also in a one-on-one conversation with GreenBiz chairman and executive editor Joel Makower.

Leading cloud computing provider Salesforce this year announced its new goal of sourcing all of its power from renewables, while Google and Microsoft also made headway toward existing all-green goals. Meanwhile, IKEA completed its 39th solar electric rooftop system in the U.S., as part of its push to attain energy autonomy by 2020.

2. EVs in the fast lane

Efforts to enable smarter, more efficient transportation systems received a palpable jolt from the success of electric vehicles in 2013. According to the most recent sales data, all-electric vehicle purchases were up about 300 percent on the year through November, with Nissan's Leaf and Tesla's Model S leading the charge. This fall, automaker Nissan delivered the electrifying news that moving the manufacture of the Leaf from Japan to the U.S. helped cut the sticker price on its all-electric car while still making a profit. 

BMW delivered its first EV in Germany in 2013, ahead of its planned U.S. sales launch in 2014, while Volkswagen announced that it will introduce 14 models of hybrids, plug-in hybrids and all-electric vehicles next year. As part of its imminent electric debut in the U.S., BMW says it will partner with California-based SolarCity to give EV buyers easy access to solar-powered charging via SolarCity's most affordable solar financing package.

Such corporate partnerships are paving the way for the continued success of EVs. In other examples, IKEA teamed up with Nissan and Ecotricity this year to install charging stations at all of its U.K. stores, while dozens of U.S. corporations — including Coca-Cola, Duke Energy, Ford, GE, GM, Google, NRG Energy and San Diego Gas & Electric — joined the Department of Energy's Workplace Charging Challenge. The collaboration seeks to vastly expand the EV charging infrastructure in the U.S. The governors of eight states added to this momentum in October when they pledged to increase the use of EVs by adding 3.3 million new electric cars by 2025. The states — California, Connecticut, Maryland, Massachusetts, New York, Oregon, Rhode Island and Vermont  — account for about a quarter of U.S. car market.

Progress for EVs and their charging infrastructure is great news for cities. Smarter, cleaner transportation systems reduce emissions in traffic-congested urban centers and could provide a clean, distributed source of peak power by tying EVs to the grid.

3. Solar after dark: storage shines

Typically, solar electric systems produce power only during daylight hours. But 2013 wasn't a typical year. A host of energy storage projects completed and initiated in 2013 could have lasting impacts on new energy systems and next-generation buildings.

In the Southwest, two new large-scale solar projects are showing one approach to enable solar electricity after dark. In Arizona, Abengoa's 280 MW Solana Generating Station came on line in October, providing up to six hours of power after the sun goes down by storing concentrated solar radiation in molten-salt tanks. In neighboring Nevada, SolarReserve, Santander and ACS Cobra Group say they are set to begin commissioning their 110 MW Crescent Dunes Solar Energy Project in Tonopah, which provides 10 hours of molten-salt storage.

While the future of such massive central station solar plants is uncertain, advocates argue that large- to mid-sized storage projects will become necessary as more intermittent solar and wind resources are added to electricity grids in coming years. In Japan, where PV grew at a record pace in 2013, numerous storage projects got under way, such as Toshiba Corp's recently announced 40 MW lithium-ion battery project in Tohoku. The project is aimed at relieving frequency fluctuations caused by variable solar power. California's new energy storage mandate also seeks to support primarily large- to mid-sized projects.

However, a more distributed vision of energy storage also advanced in 2013. In an elegant example of systems thinking (and action), Maryland's commercial microgrid combines distributed PV, battery storage, EV charging stations and LED parking lot lighting. And in California, SolarCity launched its DemandLogic service, which stores the output of rooftop PV panels in lithium-ion batteries made by Tesla Motors.

Whether large, medium or small in scale, storage was a major sustainable energy trend this year — one that appears to be just scratching the surface.

According to Navigant Research, while the annual global market for solar and wind energy storage systems was less than $150 million in 2013, it could grow to more than $10 billion over the next decade.

4. Energy efficiency building momentum

Energy efficiency gained momentum in 2013, with positive signals coming in the form of new building codes, fresh investments, new corporate commitments and innovative products cutting across industries. The efficient use of electricity "is finally starting to pull out of its decades-long doldrums," noted Amory Lovins of the Rocky Mountain Institute earlier this year, even if it is difficult to pin down actual energy efficiency spending data. 

The Johnson Controls Institute for Building Efficiency's 2013 Energy Efficiency Indicator finds that interest in energy efficiency rose sharply this year, as companies around the globe increased investments in order to save cost, while enhancing brand image and property value in the process. Established companies such as GE, Honeywell, Siemens, Tokyo Electric and Whirlpool rolled out — or committed to rolling out — smarter, more efficient appliances, lighting and energy management systems, often in partnership with innovative smaller companies, such as Nest and Opower. 

Among the major trends identified by Johnson Controls is the emergence of net-zero energy buildings, such as the new West Village at the University of California at Davis, which hopes to become the largest planned zero-net energy community in the U.S. With California's reinvigorated Title 24 building code set to take effect in 2014, new construction and restorations in the state will continue to be among the most efficient buildings in the country. And it's not just California. In October, Dallas, Texas, put the finishing touches on its new green building code. And as more architects and builders embrace green buildings in pursuit of LEED certification, the U.S. Green Building Council is also raising the bar on a new version of LEED certification.

This momentum points toward more efficient buildings designed for more resilient cities.

5. Greening the old grid

This year featured some critical milestones on the path to greening the existing power infrastructure. In Germany, wind and solar power peaked at 59.1 percent of hourly nationwide production on one particularly beautiful but blustery day [PDF] in October. In California, the state's wholesale grid operator, the California Independent System Operator (ISO), this summer recorded a record for solar [PDF] with an all-time high of 2,071 MW, or enough energy to power more than 1.5 million homes. Not coincidentally, Germany and California both seek to promote energy storage as a way of softening the impact of intermittent solar on the grid. Other countries, such as Japan, are doing the same.

Because new intermittent power capacity is still far outpacing installation of storage, operators of the old grid are turning to regulatory innovations to keep things operating smoothly. For example, California's ISO is seeking to partner with other grid operators in the Western U.S. to create the so-called energy imbalance market (EIM), in part to address increased wind and solar by sharing dispatchable resources. A rollout of the new market design was approved in November [PDF] and is set to begin together with PacifiCorp's neighboring grids in 2014.

Transporting large-scale renewables long distances in order to meet portfolio standards in the western U.S. is a major driver behind the estimated $163 billion transmission investment currently under way in North America. This includes San Diego Gas & Electric's Sunrise Powerlink and Southern California Edison's Tehachapi Renewable Transmission Project.

6. Micro-sizing a new grid

Efforts to completely reinvent the grid also grained traction. In the wake of Hurricane Sandy, several northeastern utilities increasingly reference smarter, more flexible, renewable and resilient microgrids. Konterra Realty completed one of the first commercial microgrid projects in the U.S. on the island community of Laurel, Md., this fall. The project combines advances in electric vehicles, distributed PV, energy efficiency and battery storage. Oracle Corp.'s Larry Ellison also announced plans to build a microgrid in Hawaii, while many tech firms continue to covet microgrids to power data centers.

According to Navigant Research, a total of 4,148 MW of microgrid capacity is planned or deployed throughout the world, with most activity in North America. Such projects are building momentum, with major corporations such as ABB, GE, Johnson Controls and Siemens creating software and hardware.

7. Evolving utilities: adaptation = survival

The old utility business model (making money by selling more electrons) is already being undermined by the growth of on-site, distributed energy systems and energy efficiency. A few notable utilities and energy suppliers are not only accepting this transformation, but actively pushing it forward. 

One such company is NRG Energy, a diversified power generation and retail electric supplier, which complements its large fleet of big wind and solar projects with a growing portfolio of disruptive distributed energy projects, electric-vehicle charging stations and urban renewal efforts. NRG Energy's Robyn Beavers recently discussed the transformation of the anything-but-traditional energy company at VERGE SF. Another evolving utility is the Sacramento Municipal Utility District, which is rolling out a variety of smart-grid technologies and services, including an entire solar-powered community coupled with battery-back-up.

Other large utilities, including players such as Duke Energy and PSE&G, also insist that the new distributed power paradigm is not all doom and gloom.

But the recent battle between Arizona Public Service and solar advocates over net metering this summer reinforced the notion that distributed energy is simply from Mars, while utilities are from Venus. Eventually, in November, net metering was preserved, sort of.

8. Clean energy IPOs make comeback

Global clean energy investment this year likely will fall below the $281 billion spent in 2012, according to most current data. This would be the second-consecutive year of investment decline. But one big bright spot this year was the return of clean energy investments via the public markets.

Indeed, renewable energy IPOs made a major comeback in 2013. Through September, $7.5 billion was raised in the stock-market debuts of companies such as Bluefield Solar Income Fund, Greencoast UK Wind, Infinis, NRG Yield, Pattern Energy Group, Renewables Infrastructure and TransAlta Renewables.

9. Tech giants drive renewables

Even though overall global investment in renewable energy likely was down in 2013, tech giants such as Apple, Facebook, Google and Microsoft continued to make huge commitments this year, driving renewable energy investments and installations as part of their ongoing sustainability efforts. Google was especially active in late 2013. In November, the company announced its 14th major investment into a renewable energy project by committing together with investment firm KKR $80 million to six Recurrent Energy PV projects in California and Arizona. That came on top of the $103 million that Google invested into Silver Ridge Power's 265.7 MW PV project in Imperial County, Calif., just a month earlier. In only four years, Google has invested more than $1 billion into 14 renewable energy projects.

With energy-hungry data centers, tech giants in 2013 inked many deals for renewable energy deliveries from local utilities where their data centers are housed. In September, Google signed an agreement for the entire output of the 240 MW Happy Hereford wind farm near Amarillo, Texas, for its data center in Mayes County, Okla. Microsoft signed up for all the power from the 110 MW farm near Ft. Worth for its data center in San Antonio. In addition, many technology giants are building green data centers incorporating energy efficiency and on-site renewable energy.

10. New finance models expand rooftop solar

Thanks to the financial whiz kids at San Francisco Bay Area solar companies such as SolarCity, Sungevity and others, many people who otherwise would not be able to put a rooftop solar system on their home now have one. That's because rather than selling an expensive solar electric system outright, these companies allow their customers to purchase just the energy the system produces, thus foregoing the expensive upfront equipment cost. Ownership of the system remains with the company. The response among homeowners has been overwhelming, helping the residential sector power the solar industry to its current "record-shattering year."

Mosaic extends the scope of solar power by connecting investors with solar projects in need of financing. Once the project comes online, it generates revenue by selling power, then pays back investors as revenues accrue.

Solar panels photo by Martin Nemec via Shutterstock