The clean energy and EV sectors have stormed the market with great vigor in recent times. The Invesco WilderHill Clean Energy ETF (PBW) grew 248.15 percent in the last year and it isn't alone. In this climate, Proterra — an EV bus manufacturer — is going public through a SPAC deal.The spotlight is on SPACs in 2021. There were 165 SPACs from January to October 2020, which was a new record. After Proterra announced the deal on Jan. 12, it's safe to assume that the Proterra SPAC IPO date might be one of the next in line.Proterra is going public in H1 of 2021Proterra has already announced the deal, but it may be a few months until that ticker symbol shifts. According to reports, Proterra will go public sometime in the first half of 2021. Since it's only January, investors still have some thumb-twiddling to do on the Proterra front.Proterra is merging with a SPAC called ArcLight Clean Transition, which currently trades under the ticker symbol "ACTC" on the Nasdaq Exchange. Once the deal is finalized and the newly formed company is ready for its first public trade, ArcLight will shift its ticker symbol to "PTRA."Proterra's valuation is nothing to be shy aboutCurrently, the SPAC deal estimates that Proterra is worth as much as $1.6 billion. After the merger is complete, Proterra will get upwards of $825 million in cash, which it plans to use for R&D and expansion. Backers include Chamath Palihapitiya, Daimler Trucks, and BlackRock.As of Jan. 13, ArcLight's market capitalization is at $874.12 million. The company went public last year and rose by $250 million in the IPO.Proterra is growing at a solid paceProterra, which develops battery-electric buses and EVs, has deals with 100 different public transportation agencies. One of its clients is the New York City Metropolitan Transit Authority.The company earned an estimated revenue of $193 million in 2020 and an additional $750 million in existing orders and backlogs. This constitutes a 26 percent expansion over the course of the last three years.Whatever the case, the news from Proterra has sent ArcLight stock reeling. The stock rose 67.37 percent in pre-market trading on Jan. 12. After the market opened, the stock bumped up another 23.59 percent and ultimately more than doubling from the news. Clearly, investors are already excited about this merger and want in on the action.How to buy stock from the Proterra SPACBecause we're dealing with a SPAC, investors can purchase ArcLight stock now to get ahead of the curve. After the deal goes through, investors will have the chance to hit the trading platforms for "PTRA." Once this happens, it will be just like any IPO in that most online brokerages will offer a set number of shares to access that morning.SPAC IPOs trade at a set price of $10 per share to start, so it's likely that this stock will prove less volatile than traditional IPOs. That doesn't mean it's entirely without risk (after all, SPACs can fail to merge), but the Proterra deal could be a good bet in the clean energy and transportation sectors.