Image source: Getty Images Investment trusts trade just like any other stock. I like them because they are a relatively simple way to get exposure to a large number of stocks. The Scottish Mortgage Investment Trust (LSE: SMT) is one such trust I own for exposure to tech stocks. I am considering adding the Blackrock Throgmorton Trust (LSE: THRG) to my portfolio to get broad exposure to smaller UK companies. But it’s not just stock portfolios that I can get exposure to by buying trusts. By owning The Renewables Infrastructure Group (LSE: TRIG), I get access to income and electricity-generating assets in the renewable energy space. UK small-cap stocks The manager of Blackrock Throgmorton seeks the highest-quality growth stocks in the UK small-cap space for its portfolio. The trust also takes short positions against companies that are likely to underperform, which differentiates this trust from its competitors. Performance has been good in the long term. Over the last 10 years, the trust has returned 252% versus 130% for its benchmark. However, last year the BlackRock Throgmorton share price declined by 38%. That was due to growth underperforming in a time of rising interest rates and inflation. A modest amount of gearing also amplified losses. Using data from Morningstar, I can see that the trust’s estimated net asset value (NAV) per share is 631p. The Black Throgmorton Trust share price is around 612p. That means that BlackRock Throgmorton’s portfolio is selling for about 3% less than what it is judged to be worth. And with that track record and some signs that inflation is abating, I think it is positioned to do well. I plan to start building a position this year. Investing in renewable energy The Renewables Infrastructure Group invests mainly in wind farms, but also solar and battery storage assets in the UK and Europe. It generates income from selling the electricity these assets generate. Inflation should gently nudge its revenues from existing operations higher over time. Plus the company continually seeks to add more revenue-generating assets. The UK government’s windfall tax on electricity generators will drag on income in 2023 and 2024, possibly stalling dividend growth and putting pressure on the share price. But beyond 2024 I think that dividend growth will return. And since the renewable energy industry shows no sign of slowing its growth, I am happy to hold it in my portfolio for the long term. Its share price has grown by 113% since 2013, and I hope it can repeat that kind of performance. Scottish Mortgage Investment Trust Scottish Mortgage invests in companies that are bringing transformational technologies, products, and processes to market. It chases high growth but holds for the long term to realise it. Some of these investments are in unlisted companies, and overall the portfolio is rated as a six on a seven-point risk scale according to company literature. That risk was highlighted last year when the company’s share price dropped 45.7% as the market turned away from growth stocks. But the rewards can also be great. Over the last 10 years, the Scottish Mortgage share price is up 421%. As with BlackRock Throgmorton, if inflation eases and rates stop rising, growth should come back into favour, making Scottish Mortgage a solid choice in 2023 and beyond for my portfolio.