Yes, absolutely! Here are a few guidelines to help fill in the blanks for you and for Doctor Reid:

• Prior to the first wave of volunteer citizenry, the city operated under the assumption that acts of goodwill — whether it be charitable donation, volunteerism, or simply helping ones fellow man — powered the Energem itself. The Energem has long been used to power the city, replacing the need for fossil fuels or other potentially hazardous materials in their economic infrastructure. Unsurprisingly, the city itself has a significantly lower criminal presence and a much stronger cultural emphasis on goodwill and charity than many nations we'd find in our own backyards.
  
• Over time, the city's population began to grow, thus demanding more power of the Energem than they were creating in a given period; as a result, the Energem itself sought to balance the scales. The city's administration is still trying to figure out exactly how it works, but essentially, volunteers are summoned from across the universe based on the sincerity of their wishes. In return for helping to power the Energem during their stay in the city, they are offered a piece of the Energem itself — known colloquially as wish stones — to take with them back to their home worlds.
• Wish stones may be redeemed upon returning home for a wish of the character's choosing. Since they aren't redeemed in Cadelle directly, the city administration will be admittedly a little unsure on exactly how "big" the wish can be, but they've found that wishes like preventing death, filling someone's bank account, or altering a person's own choices (ie. I wish I had never opened that door.) have all been successful. Wishes that override another person's autonomy or consent, however, have been failures — it seems the Energem, even in small pieces, is still tied to the city's moral code.
• The city has long held that acts of civil servitude and charity are powerful, but with the first waves of volunteers — they were, admittedly, pretty thirsty, as the kids say — it was discovered that physical and sexual intimacy were equally (if not more so) effective at contributing energy to the city. The administration would certainly be glad to show Doctor Reid the tracking systems that are used to determine citizen and volunteers' contributions — though, admittedly, we can't explain it very much beyond 'it's magical and it works'. (Some things just don't translate well into the literal.)
• Since the wish stone isn't redeemed until a character returns home, they don't need to decide what their contributions are going toward beyond the opportunity to make their wish of choice come true. When they're ready to return home, they'll be given a full briefing on exactly how the wish stone works, as well as how to return to Cadelle in future should they like to. (ie for canon updates and things of that sort)
• While each character's stay is different, the city has found that dedicated volunteers can earn their wish stone in as little as three months. Some do earn theirs faster — those with steady sexual partners, for example, or those who devote themselves to a full-time roster of volunteering or other constructive activities — and some do earn slower. There is no time restriction or requirement, however; the city is glad to host volunteers for as long as they'd like to stay, so long as they do not breach any of the major laws, so no murder, kidnapping, or arson, please and thank you!

We hope this helps! Please don't hesitate to let us know if you need any more information or have any future questions! ♥