This source is dependable and predictable, but more research is still needed in this area.
Completely wrong translation… 熱源 means “thermal energy”. The “source” in the English sentence means “a reference to validate the accuracy of theory/information”.
Replace 熱源 with 出典（しゅってん）or 文献（ぶんけん）if the source is a written book, report or online articles. If the source is an informant (i.e. hearsay), you cannot say 出典, so use 情報源（じょうほうげん）instead. Here is my alternative translation:
この出典 (or 文献 or 情報源) は信頼性も予見可能性も高いが、この分野でのさらなる研究が必要だ。（このしゅってん/ぶんけん/じょうほうげんはしんらいせいもよけんかのうせいもたかいが、このぶんやでのさらなるけんきゅうがひつようだ）
@msfixer, depending on which sentence is the original one, different conclusions could be made.
If we replace “source” with “heat source”, I think the sentence kind of works, but the Japanese text is not translated fully:
My translation would be:
This heat source can be safely used, predictions on the future can be made but more research in this area is needed.
Ah, I kind of see it now, my “predictions on the future can be made” has been compressed to “and predictable”.
It looks like the sentence was from a longer text, and probably the “heat” part was mentioned in an earlier part of the text.
Suppose that the overall context is talking about a new type of nuclear reactor or geothermal power generation, for example. And the single sentence was extracted from it. Yet, I still find the original Japanese sentence unnatural for the following two reasons:
If a further research is needed, you cannot say “dependable and predictable” in a definitive way at this moment. 安心して使える and 予測も立てられる in Japanese suggest that the researchers have already done with the feasibility study. It’s logically broken, and that’s why I didn’t interpret the pair as a discussion on a heat source but on a reliable reference. You need 〜しうる (may or may not; can be a good candidate) if you want to make it work in the heat source context.
Two different tones are mixed in the same sentence. 〜使えるし is colloquial while 必要である is strictly for formal/professional writings.
The cloze-word in this lesson is 熱源, so let me give you an alternative example sentence in a similar context:
(lit.) = This heat source can play a pivotal role in the stable supply of electricity. However, further research and development are required.
電力(の)安定供給 is always a hot topic in Japan because we have been suspending nuclear power reactors after 3.11 Earthquake and Tsunami in 2011. So, just memorize the term.
一翼を担う is also a common phrase in businesses. 翼 (つばさ) is “wing”. You cannot fly with only one wing, but you cannot do so without it either. 担う means “be in charge of X”. So, 一翼を担う means “to play a pivotal role”.
If you like it, feel free to add it to your own cloze collection.