诠注 - exegesis
Some relevant uses of 想 and 要, again.
想 - used as a single character,
想 can only be used in front of nouns to mean 'think about' '思考' or miss '想念'
Nouns: 我想那个。 - Intention: I want that one. Result: Fail.
Correction: 我要那个， 我想要那个。
想 can be used in front of verbs to mean 'want'
我想去上海。 Intention: I want to go to Shanghai. Result: Correct.
要 - used as a single character.
要 can be used in front of nouns to mean 'want'
我要那个。 Intention: I want that one. Result: Success.
要 used in front of verbs to mean either 'want' '想要' or will '将要'
我要去上海。 Intention: I want to go to Shanghai. Result: Success.
我要去上海. Intention: I'm going to Shanghai. Result: Success.
不想 can not be used in front of nouns to mean 'don't want'
我不想那个。 Intention: I don't want that one. Result: Failure.
不想 can be used in front of verbs to mean 'don't want'
我不想去。 Intention: I don't want to go. Result: Success.
不要 can be used in front of nouns to mean 'don't want.'
我不要那个。 Intention: I don't want that one. Result: Success.
不要 can not be used in front of verbs to mean 'don't want.' (unless you are a child.)
我不要去上海。 Intention: I don't want to go to Shanghai. Result: Fail.
想 - can't mean 'to want' in front of nouns in a positive or negative frame. In all other cases, ok.
要 - can't mean 'to want' in front of verbs in a negative frame. In all other cases, ok.
I guess this would make the 'want' use of 想 a full 能源动词, not 'defective' in any case.
And that would make 要 defective in the negative case. (At least in Standard Mandarin and some Northern dialects.) Why 要 functions successfully in the negative and positive case with nouns stems from the fact that 要 in that case is functioning as a full or regular verb, and not a 能源动词.
情态动词 与 能源动词
First of all 助动词 is 'auxiliary verb' or 'helping verb' and 情态动词 are just one type of 助动词。
I'm going to go with the thesis that the term 能源动词 is a recent invention and that 情态动词 is the original translation of the term 'modal verb' from western languages. So, 能源动词 refer to the class of verbs in chinese， english and other languages don't have this type of verb, they have a similar type of 助动词 called 情态动词. As for why they use this term 能源 I'm not clear. Also, I understand the logic of moving away from classifying these verbs as '情态动词', but they should similarly change the translation into english as well. In my dict I get the word 'volitive' which emphasizes these are verbs indictating 'will' or 'desire', but why then the 能源？ Are we supposed to take this literally as a 'source' of 'willingness'. But 能 doesn't have that feel for me。 Anyway, these 能源动词 a lot of the time aren't indicating mood in the chinese, so they probably shouldn't be called 情态动词 or 'modal verbs' in translation.
I wanted to post some youtube clip about some pop star but it is late, so you will have to wait till next time to hear me talk about 安又琪 or whatever。
From 刘月华, who we will take as the the end all and be all of all thing chinese grammar even though her book is older than the 五月花。 Why we have the term 能源动词：
1.表示愿意 - expresses intention
2.表示对情理、事理的判断 expresses one's judgment towards reason or logic
3.表示对主客观条件判断的 expresses one's judgment towards subjective or objective conditions
4.表示准许、允许 expresses permission or approval
5.表示评价 expresses a valuation
6.表示可能 expresses possibility
I guess I was just dealing too much one class of 能源动词。 李月华 also says 助动词 is just another name for 能源动词, which would mean chinese has no other types of auxiliary verbs. I'm not ready to trust her yet.