Network Working Group C. Jennings
Internet-Draft Cisco
Intended status: Standards Track March 7, 2011
Expires: September 8, 2011
Communication of Energy Pricing Information
draft-jennings-energy-pricing-00
Abstract
This specification defines media types for representing the future
price of energy in JSON. It also defines a way for a client device,
such as an electric car, to discover a web server that can provide
the future pricing for local electrical energy. This will allow the
client device to make intelligent decisions about when to use energy.
This draft is a very early skeleton of a draft to start discussion
around this idea.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 8, 2011.
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document authors. All rights reserved.
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Overview
Many uses of energy can be shifted in time. Consider charging an
electric car. When the users plugs in a car at 9pm, they may not
care when it actually charges, as long as it is ready at 8AM when
they need to go to work. This is a classic real time problem and can
be optimized as long as the charger for the car has relevant
information about how long it will take to charge and the cost of
electricity between the current time and the time when the task needs
to be complete.
This specification defines a simple JSON[RFC4627]media type to
provide the cost of energy at future points of time. It is an array
of objects in which each object contains the time a new price will
come into effect and the price at that time. JSON also defines a
well known URL on a web server so that an HTTP client can retrieve
this data. Finally as a way to automatically discover the web
server, this specification defines a DHCP option to provide the host
name of the web server.
Consider a typical residence with broadband internet and a
residential gateway that gets its IP address via DHCP from the
service provider. The service provider would provide the domain of
the local power provider via DHCP. The residential gateway would get
this and provide it in DHCP requests sent to the residential gateway.
The residential gateway would also be able to override this, so if
the consumer had arranged power from an alternative power provider,
the name of that provider could be configured in the device.
A device on the residential network, such as a dishwasher, could find
the energy provider name via DHCP. The dishwasher would then make an
HTTP GET request to the well known URI defined in this specification.
In other words, it would do an HTTP GET to the /.well_known/
energy-price.json and would receive back an energyprice+json media
type. For example
{
"currency" : "USD",
"prices":[
{ "time": "2011-04-12T23:20:00.00Z", "price": "0.028" },
{ "time": "2011-04-12T23:21:00.00Z", "price": "0.025" },
{ "time": "2011-04-12T23:22:00.00Z", "price": "0.021" }
]}
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The above example shows a case where at 21:00 UTC, the price falls
from 2.8 cents per KWh to 2.5 cents per KWh.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. Semantics
Each media type carries a single JSON object that represents a set of
prices and times. This object contains optional attributes described
below and a mandatory array of one or more measurements.
validTill: Time at which this data will become invalid. UTC time in
RFC 3339 format.
currency: Optional. Specify currency in ISO 4217 [REF] currency
code.
prices: Array of price change objects. Mandatory and there must be
at least one object in the array. Objects MUST be ordered in this
array by time.
Each price time object contains several attributes, some of which are
optional and some of which are mandatory.
time: Time this price becomes effective. UTC time in RFC 3339
format.
price: Price per KWh starting. The cost of energy changes to this
price at the time in this object and remains at this price until
the time of the next object in the prices array.
Open Issue: What is the best representation for time?
Open Issue: Is it OK that currency is optional?
Open Issue: How many entries can the array have? It would be nice
to have some maximum size.
4. Well Known URL
A client that implements this specification uses the path "//.well-
known/energy-price.json" for the resource name unless the client has
been configured with an alternative path.
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5. DHCP
Open Issues: Is DHCP the best approach to discovery or would
something else be better?
6. IANA Considerations
Note to RFC Editor: Please replace all occurrences of "RFC-AAAA"
with the RFC number of this specification.
6.1. Well-Known URI Registration
IANA will make the following "Well Known URI" registration as
described in RFC 5785:
+----------------------------+----------------------+
| URI suffix: | energy-price.json |
| Change controller: | IETF <iesg@ietf.org> |
| Specification document(s): | [RFC-AAAA] |
| Related information: | None |
+----------------------------+----------------------+
6.2. DHCP Options
TBD
6.3. Media Type Registration
The following registrations are done following the procedure
specified in [RFC4288] and [RFC3023].
Note to RFC Editor: Please replace all occurrences of "RFC-AAAA"
with the RFC number of this specification.
6.3.1. energyprice+json Media Type Registration
TBD
7. Security Considerations
TBD
Further discussion of security proprieties for media types can be
found in Section 6.3.
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8. Privacy Considerations
TBD
9. Acknowledgement
I would like to thank someone for their review comments.
10. Normative References
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December 2005.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Author's Address
Cullen Jennings
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Phone: +1 408 421-9990
Email: fluffy@cisco.com
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