"Wasting" Hydro Power?

Alacrates's picture

I'm not sure if anyone on the forums knows a lot about hydro power, I'm trying to figure out the energy situation that I'm living within (Winnipeg, MB, Canada), which rely's on hydro power exclusively for electricity (and natural gas for a lot of our heating.)

Are there ecological downsides to "wasting" hydro power?

I know there are environmental problems with setting up dams to create hydro power. And of course, from a personal standpoint, the less power that you use, the less that you have to pay for, and the more resilient you are overall.

Beyond that though, I'm wondering if there is any particular virtue in using less electricity in a hydro powered system. (I happen to live in an apartment where utilities are just part of the rent, you don't pay for what you use beyond that.)

I'm thinking that the turbines at the hydro stations are turning continuously no matter what, generating voltage regardless of whether we make use of it or not. It seems like a very different situation than a power plant that uses coal or natural gas to create electricity - in that case, if the region kept their usage low, less fossil fuels would be consumed, less GHG would be emitted into the atmosphere.

I know that Manitoba does sell some power outside the province, so I'm thinking there might be benefit to conservation there, if we could supply more hydro power to an area that is relying on fossil fuel generated power.

Anyways, just wondering if anyone had any thoughts on this issue, thx.

Sweet Tatorman's picture

You write >I know that Manitoba does sell some power outside the province, so I'm thinking there might be benefit to conservation there, if we could supply more hydro power to an area that is relying on fossil fuel generated power.<
This is in fact the case for your utility. Manitoba Hydro exports about one quarter of all electricity generated and most of that amount to northern US States with potential to be displacing fossil generation. I don't know about the lesser amount being exported to adjoining provinces.
You write >I'm thinking that the turbines at the hydro stations are turning continuously no matter what<. This is not correct. Large facilities have multiple turbines that are operated or not depending upon demand. Also for an operating turbine some designs permit operation down to less than 50% of nameplate with only small reduction in efficiency thus water flow is proportional to power generated. A quick Google on your utility reveals that their 3 largest stations each have 10 to 12 individual turbines so lots of operational flexibility there. With the exception of "run of the river" installations which have negligible reservoir storage, hydro installations of any size typically have substantial reservoir storage so any water not used in the moment remains available for use later. Since Manitoba Hydro has capacity well in excess of the needs of the Province this stored water is "Money in the Bank" as the export sales of electricity are a non-tax source of revenue to the citizens since Manitoba Hydro is owned by the Province.
You are in an enviable position of living in a Province were essentially all of the generation is renewable with extra to use to generate a bit of revenue.

Alacrates's picture

Thanks kindly for the reply - I have asked a few people this question, and have never got a really clear reply (maybe that is due to my own lack of understanding of power generation!) I do have an older book on hydro electric power stations that I have been meaning to get through, but it just hasn't made it to the top of the pile yet!

A few questions on your reply, if you have the time:

"Large facilities have multiple turbines that are operated or not depending upon demand" Do they activate these turbines to try to match exactly the requirements for the power that is being used? (so if we Manitobans are drawing a certain amount of amperage at certain voltages, they have to match that number at the power stations?)

Or is there a benefit to the turbines to keeping them out of energy production (something like wear degrading them) or it is about not drawing water pressure from the dammed water? (I appreciate if this question is confused & you don't want to pull it apart, I can wait until I get to that hydro-power book for answers!)

"Also for an operating turbine some designs permit operation down to less than 50% of nameplate with only small reduction in efficiency thus water flow is proportional to power generated. " I don't understand this at all, is there any way to describe this in different terms?

Last, from an individual Manitoban's viewpoint, would the main ecological benefit of reducing electrical consumption be that we can sell more of the electricity generated to places where fossil fuels are used to generate energy, and therefore prevent the release of some of those GHG's? I ask this because I've been in several transition/environmental groups, and I have several ways of decreasing one's electrical usage in daily life, I just want to be clear on the rationale for doing so (I'm not sure anyone in the group is clear on this point!)

I don't know a lot about Manitoba Hydro, but I mostly hear complaints about it: there are groups that say that it has caused a lot of problems for the native/indigenous peoples who live in northern part of our province. They also don't like the rate hikes that MB Hydro is proposing for electricity, and the costs for the new Keeyask Generating Station. There is also a lot of controversy about the workers who built these stations, regarding their interactions with the local populations around these sites.

Anyways, it is a lot of confused information around these projects that is coming to me. (I'm trying to finish an apprenticeship as a plumber at the moment, so this information is a little off to the side for me a the moment, but I mean to come back to it.) Thanks again for your reply.

Sweet Tatorman's picture

You write: >"Large facilities have multiple turbines that are operated or not depending upon demand" Do they activate these turbines to try to match exactly the requirements for the power that is being used? (so if we Manitobans are drawing a certain amount of amperage at certain voltages, they have to match that number at the power stations?) <
Generation is matched with demand since electricity is not stored within the system. At a given demand some number of turbines will be generating at there design nameplate capacity and a smaller number will be operating at below design capacity so that they are already up to speed and connected to the grid. The ones operating at part load are capable of responding quickly to changes in demand by means of admitting more or less flow into the turbine by means of adjusting components generally referred to as gates or wickets. Conceptually, if you turn on a light in your apt the flow into a turbine on the grid will be increased to supply that additional load. In practice, it is the aggregate change in demand of all the customers added or subtracting demand that determines the change in flow into the turbine. For system stability and reliability it is required to have a certain amount of "spinning reserve". For example, if a turbine with a nameplate capacity of 100MW is currently generating 60MW the other 40MW of capacity is considered to be spinning reserve. Spinning reserve is capable of rapidly responding to increase in demand unlike units which are shutdown which require considerable time to bring up to speed and connect to the grid.

You ask >Or is there a benefit to the turbines to keeping them out of energy production<
Generally a turbine is most efficient when operating at or near full capacity. It is therefore the most efficient use of the available water resource to have most of the operating turbines at full capacity and only the lesser quantity at part capacity as needed to meet the requirement for spinning reserve.
You write >"Also for an operating turbine some designs permit operation down to less than 50% of nameplate with only small reduction in efficiency thus water flow is proportional to power generated. " I don't understand this at all, is there any way to describe this in different terms<
An example: some turbine designs take a big efficiency hit if operated at part load, say using 90% of the water to generate 50% of the power. Others do better, say using 55% of the water to generate 50% of the power. Clearly it is the second type that would be more desirable to provide the spinning reserve.
You ask >Last, from an individual Manitoban's viewpoint, would the main ecological benefit of reducing electrical consumption be that we can sell more of the electricity generated to places where fossil fuels are used to generate energy, and therefore prevent the release of some of those GHG's?<
Yes.

Alacrates's picture

Wow, thanks again SweetTatorman, you do know your stuff... I'm sure there are people nearby who know the details of this type of power generation, but I've had trouble asking these questions in the environmental groups that I've been in... I do have a more study to do to make these systems clear to me, but these answers are quite helpful, thx.

lathechuck's picture

I've found that people who are most vocal about environmental issues are often uneducated about the "amps and volts" of the energy technology they contemplate. I'm glad you're helping to bring out the details that can help the general population discriminate between the feasible and merely xwishful responses to our energy supply predicament. You can't go wrong by reducing demand, regardless of your source, because (as you recognized from the beginning), power produced in excess of local needs can be transmitted elsewhere, where it will displace some other source. Like hydro though, coal and nuclear power stations do not react quickly to changes of load, so the quickest response might be to feather the blades of a wind turbine! (That will reduce wear on the gear box, but doesn't do much about CO2). A better idea is to use hydro to respond to fluctuations in wind and solar power (when they become significant), so reserve as much water in your reservoir as you can, until you can charge a premium price for energy exports.