A smart beta exchange traded fund, the Invesco Global Clean Energy ETF (PBD) debuted on 06/13/2007, and offers broad exposure to the Alternative Energy ETFs category of the market.What Are Smart Beta ETFs?Market cap weighted indexes were created to reflect the market, or a specific segment of the market, and the ETF industry has traditionally been dominated by products based on this strategy.A good option for investors who believe in market efficiency, market cap weighted indexes offer a low-cost, convenient, and transparent way of replicating market returns.But, there are some investors who would rather invest in smart beta funds; these funds track non-cap weighted strategies, and are a strong option for those who prefer choosing great stocks in order to beat the market.Based on specific fundamental characteristics, or a combination of such, these indexes attempt to pick stocks that have a better chance of risk-return performance.Even though this space provides many choices to investors--think one of the simplest methodologies like equal-weighting and more complicated ones like fundamental and volatility/momentum based weighting--not all have been able to deliver first-rate results.Fund Sponsor & IndexBecause the fund has amassed over $400.10 million, this makes it one of the average sized ETFs in the Alternative Energy ETFs. PBD is managed by Invesco. PBD seeks to match the performance of the WilderHill New Energy Global Innovation Index before fees and expenses.This Index is an index comprised primarily of companies whose technologies focus on the generation and use of cleaner energy, conservation and efficiency & the advancement of renewable energy in general, as determined by WilderHill New Energy Finance, LLC.The New Energy Global Index is mainly comprised of companies in wind, solar, biofuels, hydro, wave & tidal, geothermal.Cost & Other ExpensesCost is an important factor in selecting the right ETF, and cheaper funds can significantly outperform their more expensive cousins if all other fundamentals are the same.Annual operating expenses for PBD are 0.75%, which makes it one of the most expensive products in the space.The fund has a 12-month trailing dividend yield of 0.55%.Sector Exposure and Top HoldingsIt is important to delve into an ETF's holdings before investing despite the many upsides to these kinds of funds like diversified exposure, which minimizes single stock risk. And, most ETFs are very transparent products that disclose their holdings on a daily basis.When you look at individual holdings, Solarpack Corp Tecnologica Sa (SPK) accounts for about 1.07% of the fund's total assets, followed by Jinkosolar Holding Co Ltd Adr (JKS) and Sunrun Inc (RUN).The top 10 holdings account for about 9.78% of total assets under management.Performance and RiskYear-to-date, the Invesco Global Clean Energy ETF has lost about -19.12% so far, and is up about 56.76% over the last 12 months (as of 07/28/2021). PBD has traded between $18.09 and $40.71 in this past 52-week period.PBD has a beta of 1.22 and standard deviation of 31.37% for the trailing three-year period, which makes the fund a high risk choice in the space. With about 141 holdings, it effectively diversifies company-specific risk.AlternativesInvesco Global Clean Energy ETF is a reasonable option for investors seeking to outperform the Alternative Energy ETFs segment of the market. However, there are other ETFs in the space which investors could consider.IShares ESG Aware MSCI EM ETF (ESGE) tracks MSCI Emerging Markets ESG Focus Index and the iShares ESG Aware MSCI USA ETF (ESGU) tracks MSCI USA ESG Focus Index. IShares ESG Aware MSCI EM ETF has $7.37 billion in assets, iShares ESG Aware MSCI USA ETF has $20.43 billion. ESGE has an expense ratio of 0.25% and ESGU charges 0.15%.Investors looking for cheaper and lower-risk options should consider traditional market cap weighted ETFs that aim to match the returns of the Alternative Energy ETFs.Bottom LineTo learn more about this product and other ETFs, screen for products that match your investment objectives and read articles on latest developments in the ETF investing universe, please visit Zacks ETF Center. Zacks Names "Single Best Pick to Double" From thousands of stocks, 5 Zacks experts each have chosen their favorite to skyrocket +100% or more in months to come. From those 5, Director of Research Sheraz Mian hand-picks one to have the most explosive upside of all. You know this company from its past glory days, but few would expect that it's poised for a monster turnaround. Fresh from a successful repositioning and flush with A-list celeb endorsements, it could rival or surpass other recent Zacks' Stocks Set to Double like Boston Beer Company which shot up +143.0% in a little more than 9 months and Nvidia which boomed +175.9% in one year.Free: See Our Top Stock and 4 Runners Up >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Invesco Global Clean Energy ETF (PBD): ETF Research Reports JinkoSolar Holding Company Limited (JKS): Free Stock Analysis Report Sunrun Inc. (RUN): Free Stock Analysis Report iShares ESG Aware MSCI EM ETF (ESGE): ETF Research Reports iShares ESG Aware MSCI USA ETF (ESGU): ETF Research Reports To read this article on Zacks.com click here.