NRG Energy, according to its website, is offering airports, malls, sport venues, and similar public locations a service which allows customers to "rent" lockers in which they can charge their mobile devices securely.

At least some of the kiosks provide free charging, as indicated by this instagram photo. Whether this policy is universal, or venue-specific, is not clear.

NRG's "SureCharge" service allows customers to plug in their phone, lock it up and walk away (due to TSA regulations, the airport kiosks do not offer lockers, so the customer must remain with the device while charging). The lockers differ from NRG's other portable power solution, its Pivit Point stations, which rent portable chargers which the customer can carry with them so they can continue to use their mobile device while charging.

See a picture of the locker kiosk below -- note the branding of Reliant on the kiosk

SureCharge lockers are compatible with iPhone, iPod, Blackberry, Android and Windows phones, "and you can find them in airports, sporting venues and retail centers throughout the U.S.," NRG says.

Additionally, NRG has now announced further permanent installations of its Pivit Point portable power stations, which rent mobile charging devices. Aside from NRG park, the Pivit Point website now lists permanent installations as including:

• George R. Brown Convention Center (Houston)

• Lucky Strike, Bowling (Houston)

• Celtic Gardens, Restaurant (Houston)

• Pub Fiction, Restaurant (Houston)