HARVARD -- For avid biker James Porter, it's not about the miles per hour. It's the smiles per hour.

Drivers along Route 2A or Barnum Road might see Porter in a curious-looking pod chugging along the roadside. The vehicle is actually a velomobile, a three-wheeled bike powered with the combination of an electric motor, solar energy and, of course, his own two feet.

The Devens resident is back on the road after recovering from an operation on his arthritic knee, pulling the savvy vehicle from the "mothballs" he said it's been sitting in since 2000.

Encased in a protective covering, Porter sits in the bike much like he would in a car.

Equipped with an emergency brake, a throttle knob to rev the engine and his own make-shift stereo system, it's almost as though he were in one.

The engine sits in the back, along with a sort of trunk where Porter can store his things. The front of the vehicle has room for a solar panel that helps charge the batteries for the motor, although Porter has not installed it yet. He attached a GPS device to his windshield, which is even equipped with a little wiper.

The velomobile can help Porter reach a speed of 20 miles per hour, around the state's 25 mph speed limit for motorized bicycles.

Since Earth Week began two weeks ago, Porter has been commuting roughly 8 miles to his job at Carlson Orchards all on with his own power. He has not yet re-installed the motor that could give him the extra push through Harvard's hills.

"With the big hills and my knee not being in top shape either, it takes some time," he said. "But I love riding my bikes, and the more time it takes, the more fun I'm having."

Porter first received the bike on Earth Day 14 years ago when he did a publicity tour for Zapworld.com, the website for a company that makes electric vehicles.

He had been doing well as an endurance bicyclist -- with a preference for 24-hour races, he would ride 400 miles in one day.

But he wondered how he could go even faster, and when he was introduced to an electric bike in the '90s, he went 607 miles in 24 hours.

From there, he rode a Zapworld bike in the American Tour de Sol in 1995. The event, Porter said, was a "semi-competition rally."

"That was actually right before the Prius was coming out, so it was not a competition but a showcase," he said.

Later that same year, he set a few records in a world solar bike race in Japan. The next year, he went as more of a coach figure, bringing a ZAP bike kit to Japan to construct bikes there for an American women's team.

When his knee problems started four years ago, he still didn't stop, riding hand-powered bicycles while he recuperated.

"I entered two races with hand-power, again for my own health," he said. "I just need the wind in my hair to keep me sane."

Last spring, he found a donor match for a knee tissue transplant from a family of a 12-year-old boy who passed away. Porter is still doing physical therapy exercises and will eventually need surgery in his degrading left knee, he said, but he is trying to get his strength back up to do some more racing.

For now, though, biking for Porter is just about feeling good.

"People are always wondering, 'Why are you doing it? What are you promoting? What for?'" he said.

He could dedicate his riding to raise awareness about drunk driving, as he has been hit by a drunk driver himself. He has also been in races where a drunk driver has killed fellow riders, he said, "but I didn't want to dedicate my life to stopping something."

"I'm more of a person who likes to promote something," he said.

Promoting tissue donation would be great, he said, but the main topic he's focused on is promoting health.

"Starting with my own health, and then going on to other people's health in my community," he said. "And then on top of that the earth's health. I think it's all related."

Porter's new commute times perfectly with National Bike to Work Week, coming up on May 12. With one knee in recovery and another one still needing work, Porter's continued cycling makes him a great biking advocate.

"I'm not out there saying you have to do this, you need to do this, you should do this," he said. "I'm saying I'm doing this, and I'm getting these benefits from it."

Biking makes him feel good, he said, and if others want to do it, they certainly can if he can.

"If I help you make the decision to ride your bike to work, or just for fun on the weekends, then that makes me feel good about what I'm doing," he said.

Follow Amelia on Twitter and Tout @AmeliaPakHarvey.